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Posted on Jan 15, 2010 in Tactics101, War College

Tactics 101 045: The Passage of Lines

By Rick Baillergeon and John Sutherland

Beginning this month, we will spend the next few articles discussing what are termed tactical enabling operations. As the name implies, these operations set the conditions to conduct a larger mission later. Within this group you will find missions such as passage of lines, relief in place, encirclement, etc… Clearly, these are extremely challenging operations and demand the utmost in quality planning, preparation, and execution in order to have the possibility of achieving success. 

We will start our look at these enabling operations with a discussion on the passage of lines. At first glance, this operation appears straight forward and relatively easy to execute. However, as we have all heard many times, ‘looks can be deceiving’. In reality, the passage of lines is extremely challenging and takes a highly trained and skilled unit to execute it successfully. Our study of the passage of lines will look at the following areas: 1) Definition 2) What is the purpose of a passage of lines 3) Planning, Preparing and Executing a Passage of Lines 4) The command and control of a passage of lines and 5) The types of passage of lines (with discussion on each). Let’s move out!

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WHAT IS A PASSAGE OF LINES?

In simple terms, it is an operation when one unit maneuvers through another unit’s positions in order to pursue the enemy or to get out of enemy contact. It is an operation relying on a combination of detailed coordination between units, well-planned and understood control measures, a defined command and control structure and the utmost flexibility in planning and execution. 

Throughout military history, there are numerous examples were the successful execution of a passage of lines was the determining factor in future victory. It may have enabled a unit to exploit success against its’ opponent by maneuvering combat power forward at the right place and right time. Vice versa, if things were not going well for a unit; the ability to break contact from the enemy allowed them to be utilized at another time. In either case, the execution of the passage lines sets the conditions for future success.

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WHY?

There are numerous reasons for the necessity to conduct a passage of lines between units. These include:

· A window of opportunity presents itself to exploit offensive success against the enemy. Thus, forces may be maneuvered forward of their current positions and maneuver through stationary forces. These forces may execute a counter-attack, envelopment, or pursuit in this window of opportunity.

· Because of the terrain or time constraints, it may not be feasible to bypass a stationary unit.

· A unit has completed a mission such as a screen or covering force and now has been ordered to fall back to positions in the rear area.

· A unit is losing significant combat power and must break contact with the enemy before becoming decisively engaged.

· The forward unit has been ordered to conduct a retrograde operation (delay, withdrawal, or retirement).

· Free the unit for use somewhere else on the battlefield.

· Sustain the tempo or momentum of an offense.

TYPES OF PASSAGE OF LINES

To no one’s surprise, there are two basic types of passage of lines – forward and rearward. Not to insult anyone’s intelligence, but here are the differences: In a forward passage of lines, a unit maneuvers through another unit’s position towards the enemy. This maneuver is normally tied to an offensive action against the enemy. In a rearward passage of lines, a unit maneuvers through another unit’s position away from the enemy. This maneuver is normally tied to preserving the unit’s combat power for a future use or the unit has just completed a mission against the enemy.

WHO’S IN CHARGE?

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As mentioned above, effective command and control during the planning, preparation, and execution of a passage of lines is vital to success. There can’t be any gray area as to who is in charge and who is responsible for what actions during a passage of lines. With that in mind, there are three key components in the command and control structure. These are the passing (maneuvering) commander, the stationary commander, and the higher commander (both the passing and stationary commanders fall under him). Each of these commanders has specific roles during the planning, preparation, and execution of a passage of lines. Below we will define some of the key roles each commander (and of course his staff) plays in the passage of lines.

The Higher Commander

· Normally determines the specific location and time of the passage of lines.

· Generally develops the control measures required to execute the passage of lines.

· Overall responsibility for the conduct of the operation.

· Develops an Operations Order to initiate planning and preparation and assists in overseeing execution.

· Provides the Stationary and Passing Commander with any resources needed to execute the operation.

· Determines subsequent missions for units involved in the passage of lines following its’ completion.

· Receives briefbacks from both Commanders once they have received the mission. Depending on the tactical situation these could be conducted face to face or through the use of technology.

The Stationary Commander

· If the tactical situation warrants (little planning time available) may determine the location and time of the passage of lines.

· If the tactical situation dictates (little planning time available) develops control measures and a brief fragmentary order to facilitate the operation.

· On rearward passage of lines, normally assumes responsibility for the area previously occupied by the passing unit once 2/3 of the passing unit’s combat power is through the passage point.

· Determines location for co-location of command posts during the passage of lines.

The Passing (Maneuvering) Commander

· On forward passage of lines, normally assumes responsibility for the zone of attack after 2/3 of its’ combat power is through the passage point.

PLANNING CONSIDERATIONS FOR A PASSAGE OF LINES

Although a passage of lines can be a relatively no notice event; it is critical units maximize whatever planning time is available. Within their planning, there are several things that must be addressed to assist in successful execution. We will highlight several of these subjects below.

a. Organization of Forces. When organizing forces (in particular the passing force) there is no need to reinvent the wheel. As much as possible keep unit integrity during the passage of lines. This minimizes confusion, which in turn should directly correlate to smoother execution. It also assists in quicker execution during the follow-on mission.

b. Order of Movement. A passage of lines is not an ends to itself. Consequently, you want to come out of a passage of lines set to execute your mission. For instance, if you were conducting a forward passage of lines to execute an attack against the enemy; you would want to be positioned to conduct the attack. With that in mind, during the planning you want to get your key combat units through the passage first. Backwards planning assists you in achieving this. Decide how you want to look to begin the attack. Then, determine how the passage of lines must be executed to accomplish this.

c. Control Measures. One of the most important actions during planning is to determine the control measures required to execute the passage of lines. These control measures will be utilized by all units involved in the passage. There can not be one set of control measures for the passing unit and another for the stationary unit. We all know how that turns out! Below we will provide an example graphically of the most critical control measures and then discuss each. We will utilize a forward passage of lines for the example. However, the basic principles apply to a rearward passage of lines as well.

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In our discussion, let’s work from south to north.

AA (Assembly Area) KHAKI – This is the designated assembly area for the passing unit. The tactical situation will dictate how long the passing unit will occupy the assembly area. Normally, the time period is not long because you want the passing unit to get forward and exploit a window of opportunity.

SP (Start Point) A/B/C – These are the start points for the routes the passing unit will utilize to maneuver through the stationary unit’s positions. In most cases, the stationary unit will provide guides to assist in making this as smooth as possible. The passing units will also be under command and control of the stationary unit. 

Routes – Under the command and control of the stationary unit, the passing unit utilizes routes to pass through the preponderance of the area. The route will begin at the SP and end at the RP. Obviously, the more routes designated, the quicker the passing unit can maneuver through the stationary position. There should be primary routes and alternate routes planned. Alternate routes may be needed depending on the tactical situation.

RP (Release Point)1/2/3 – These are designated release points at the end of the route. The release point is the place on a route where passing units come back under the control of their respective commanders. 

Passage Lanes – On our above example, passage lanes have been designated after the release points. These passage lanes are lanes through an enemy or friendly obstacle that provides safe passage for a passing force. The lane may be cleared, including being reduced and proofed, as part of a breach operation, or it may be included as part of the design of a friendly obstacle. It is a clear route all the way through an obstacle. Again, these lanes assist in passing through the unit as quick and smoothly as possible. You will want to designate primary and alternate passage lanes.

FEBA (Forward Edge of the Battle Area) – Within a passage of lines, this is forward location of the stationary unit’s combat forces. This does not include the stationary unit’s recon forces. This is important for command and control and for coordinating fire support.

PP (Passage Point) 4/5/6 – In essence, once the passing unit (in a forward passage of lines) moves through the passage point they have control of the terrain forward of them. Thus, the passage point is critical in determining command and control of terrain.

ATTACK AXIS MIKE/DALE/STEVE – In a forward passage of lines, the objective is normally to set the conditions for the passing unit to conduct an attack. With this in mind, attack axis should be determined so the unit can quickly maneuver into attack formations. These attack axis are generally developed just forward of the passage point. 

PHASE LINE GREEN — Phase Lines are important for controlling maneuver and for assisting in situational awareness and understanding. In developing phase lines, anticipate future operations. Consequently, they should be drawn forward in anticipation of success and facilitate the next mission. 

OBJECTIVE ORANGE – If you are going to attack, there must be an objective (be it terrain or enemy focused). In the above example, the forward passage of lines is conducted to set the conditions for the passing unit to maneuver and achieve a purpose and task on OBJECTIVE ORANGE.

There are other control measures (not depicted on our graphic) that may be of value or needed during a passage of lines. These include:

Contact Point — If the passage of lines is relatively no notice, a contact point may be needed to not only conduct any coordination, but to actually begin the passage. As a reminder, a contact point is a place on the ground where two or more units are required to make physical contact. If this is the place where the passage will begin then the stationary unit positions guides to help the passing unit maneuver through them. You should not develop contact points that are within enemy direct fire range or observation. Clearly, this can be a very lucrative target.

Battle Handover Line – Always knowing who is in charge is critical on the battlefield. In the case of the passage of lines, sometimes this can get a little dicey. To assist in this, we develop a phase line and designate it the battle handover line. This location is where one unit assumes responsibility from another unit for the conduct of a battle. If required, the stationary unit must be able to engage out to this line and help the passing unit disengage.

Recognition Signals – Although it is not found on a set of graphics, understood recognition signals (by both passing and stationary units) are critical. A passage of lines can be a very chaotic operation. Despite all the high tech systems available, a simple recognition signal may be the difference between mission accomplishment or failure. Recognition signals can take the form of letters, words, visual displays, characters, signal flags, or special lights/sounds with prearranged meaning. Again, both the stationary and passing units must understand what the signal mean. This can be easier said than done!

Below you will find some simple graphics containing the essential control measures for a rearward passage of lines.

Figure 2-1. Control Measures for a Rearward Passage

d. Fires Planning. During the planning of fires, ensure the direct and indirect fire plans of the stationary and passing units are integrated. In an operation such as this (especially if a unit is forced to conduct a hasty rearward passage of lines), indirect fires can buy you time and prevent casualties. If the fire plans are not tied in, time can be lost in sorting details out.

e. Reconnaissance Planning. One of the most important parts of planning is in the area of reconnaissance. This is especially critical during a forward passage of lines. The stationary unit can provide vital intelligence to the passing unit which can greatly assist during their eventual attack. Key in the planning process is the handover of reconnaissance between the stationary and passing unit scouts and intelligence assets. This must be a seamless transition so there is no break in intelligence gathering and analysis.

f. Terrain Management. As we all know, land is valuable. Within a passage of lines, it is important there is a well-thought plan for terrain occupation. This is especially true if the passing unit must occupy assembly areas prior to conducting the passage or after conducting the passage.

g. Combat Service Support. You can not overlook combat service support planning within a passage of lines. There are many moving pieces during the operation. In the context of vehicles – things are going to break. There must be an understood plan as to who will evacuate vehicles and casualties. 

PREPARATION OF A PASSAGE OF LINES

Thorough preparation is critical in any mission to set the conditions for success. This is certainly true in a passage of lanes. Preparation time is at a premium, so every minute must be used to its fullest. During this preparation time, there are several actions, that if effectively executed will aid tremendously in mission accomplishment. Let’s highlight these below:

a. Coordination. Coordination between units is significant in any operation. Within the context of a passage of lines, it is imperative. Communication is a must and there are numerous items that should be coordinated. Let’s address the items that are normally addressed during the coordination between the stationary and passing units. These include:

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* Exchange of Intelligence. Sharing of intelligence is important and there are numerous examples where this set the conditions for mission success. Exchange of intelligence is especially crucial in a forward passage of lines. The quality of intelligence a stationary unit shares with the passing unit will truly assist them in conducting a follow-on attack.

* Exchange of Tactical Plans. No matter the type of passage of lines (forward or rearward), it is important all units know the tactical plans (current and future) of all units involved. You clearly do not want the execution of the passage to negatively affect the ability of the stationary unit to accomplish their mission. There should be no surprises!

*Where are the Obstacles? Nothing can derail a passage of lines quicker than the passing unit running into an obstacle they did not know existed. The passing unit must know the location of all obstacles within the area of operations. This includes any obstacles emplaced forward of the passage of lines that the passing unit may maneuver through during their subsequent attack. This discussion should also include items such as the locations of enemy obstacles, of existing lanes and/or bypasses, and of guides for the passage.

* Not so Mundane Details. The passing unit must share details such as unit designation, vehicle composition and number of vehicles that will pass with the stationary unit and the anticipated time of the passage.

* Exchange of Signal Instructions. During the passage, it is wise for both the passing and stationary unit to share a common radio frequency. Hopefully, this is an unassigned frequency that can be utilized. If one does not exist, the passing unit may move to the stationary unit’s frequency during the passage. Included in signal coordination should be items such as recognition signals (near and far), passwords, etc…. 

* Potential Actions on Contact. During coordination, leaders from the involved units should wargame the what-ifs. Units must know the anticipated actions if the enemy attempts to hinder the ability of the passing unit to conduct the passage.

* Handover of Reconnaissance. There must be a clear understanding of the time and place of reconnaissance handover. This has to be as smooth as possible so there are no breaks in gathering intelligence.

* Security Measures. There should be coordination as to the actions and responsibilities if the area comes under a nuclear, biological, or chemical attack.

* Command and Control Changeover. Units must determine the time or circumstances during which responsibility for the control of the area of operations is transferred

* Specific Passage Details. This includes priorities for routes and facilities, including provisions for movement control.

* Fire Support. In such a dynamic environment, it is imperative responsive fire support is available. Fire support may be the only asset you possess that can buy you vital time or attrite the enemy. Thus, the fire support elements of both the stationary and the passing unit must agree on allocating firing positions. The Stationary Commander controls the allocation of firing positions in case of disagreement. These positions must be far enough forward to support the operation without having to redeploy during critical stages of the battle. All forces must know the fire support control measures established.

*Combat Service Support. The stationary unit is normally responsible for the logistical needs of the passing unit. This could include medical, maintenance, and recovery assistance. During coordination, units should anticipate some of these requirements. This can facilitate pre-positioning supplies so they are there when needed.

* Agreeing on Maneuver Control Measures. During planning, graphics (hopefully) were developed to assist in executing the passage of lines. During coordination, units should ensure that the planned control measures are adequate for the operation. If they are not, then changes are required. 

b. Co-locate Command Posts. One of the best ways to facilitate coordination, is for the stationary and passing units to collocate command posts. There are several options that can be utilized. First, if there is sufficient time, you may co-locate the main command posts of each unit. Clearly, this allows the most communication. However, co-locating could produce a large physical signature on the ground and electronically through the air. Second, units may co-locate their tactical command posts. These are smaller elements and normally are comprised of elements of all the battlefield operating systems. Finally, if time is at a premium, the passing unit may send an LNO (liaison) team to the stationary unit command post.

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c. Rehearsals. In any operation, a well-orchestrated rehearsal will pay dividends during execution. Obviously, the key factor in conducting any rehearsal is time available. As discussed earlier, prep time may be minimal before the execution of a passage of lines. However, the prudent Commander will carve out whatever time is available to conduct some type of rehearsal. Clearly, it will not be a full-up rehearsal. But a good radio rehearsal can be of great value. 

DISSECTING THE TYPES OF PASSAGE OF LINES

Earlier in the article, we highlighted the two basic types of passage of lines – forward and rearward. Below we will address some keys to success for each.

FORWARD PASSAGE OF LINES

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· Perhaps, the most important piece of terrain in the entire operation is the area forward of the actual passage point. The stationary force must ensure they have control of this area and it is large enough for the passing unit to move into attack formation. If this turns into a bottleneck, it will soon become an enemy artillery magnet.

· The passing force must set the conditions for their subsequent attack following the passage. This means the passing force is already organized for an attack prior to the actual passage. If the passing unit must halt after the passage to get into this organization they will likely lose their window of opportunity. If they do halt, they again become an artillery magnet and highly susceptible to enemy attack.

· Normally, support by the stationary force will stop once the passing force maneuvers past the direct fire range of the stationary unit’s weapon systems. Depending on the tactical situation, fire support and air defense support may continue.

· Deception operations are difficult to achieve in a passage of lines. There usually is just not enough time to make it believable and get the right assets in place to make it work. Depending on the weather, the proper use of smoke can be of value. In this case, smoke is generally used for security purposes vice deception purposes. 

· In a forward passage of lines, have your attack helicopters (if available) on a short lease. They can get you out of jams and the what-ifs.

· Air Defense is crucial during a forward passage of lines. With two units positioned in a relatively small area; this can make for a lucrative target for enemy aircraft. During the passage, the stationary unit will be responsible for air defense

· Electronic Warfare can be a huge combat multiplier during the passage. These operations should be directed against enemy command and control nodes and fire support nets. 

· If you plan to shoot any artillery prep fires; the best time is when the passing unit begins maneuver to the passage lanes. Again, the stationary unit has responsibility for firing any prep fires.

· During a forward passage, do not forget the potential impact of prisoners of war and displaced civilians. Each can tie up your assets and can clog up passage routes.

REARWARD PASSAGE OF LINES

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· The key differences between the forward and rearward passage are:

o In a rearward passage, the enemy normally has the initiative. Because of this there is much less time available for planning and preparation. 

o In most cases, the passing unit Soldiers (in a rearward passage) are both physically and mentally tired. This must be taken into consideration during planning. The simpler the plan – the better.

o In a rearward passage, you must consider the fact that enemy forces could be intermixed with the passing forces. 

· In a rearward passage, it is imperative there is handover in the area of reconnaissance. As the passing unit recon elements fall back, intelligence responsibilities must pass to the stationary unit. If not, a serious intelligence gap can result.

· As the passing unit passes through any stationary unit obstacles; the stationary unit must ensure obstacles are closed.

· The usual order of march in a rearward passage is almost directly opposite of a forward passage. You will normally find it to be: combat service support units, main command post, combat support elements, tactical command post, and combat units. The rationale is to get your logistics in place at the other end first. This enables them to get established so they can refit, refuel, and rearm forces that have probably been involved in significant combat.

· During a rearward passage, the stationary unit must be prepared to facilitate maneuver with accurate and responsive direct and indirect fires. There are many examples where these fires were the difference between the unit successfully conducting the passage and being decisively engaged by the enemy.

· Within fire support, it is critical that mechanisms are in place so the stationary unit can answer any calls for fire by the passing unit.

· Within the passage, the stationary unit’s engineers must be prepared to assist in the passing unit’s maneuver. The main priority for these engineers is normally ensuring the passing unit is able to maneuver through the passage lanes to the release point.

· The effective use of smoke can greatly assist in concealing the maneuver of the passing unit. 

· The stationary unit must be prepared to assist the passing unit in all logistical areas. This includes medical, recovery, fuel, supplies, and ammunition.

· The execution of a rearward passage of lines can be a very chaotic time. With this chaos brings a greater risk for fratricide. To mitigate this risk, it is key that recognition signals are established and understood by all units involved in the passage.

SUMMARY

Within this article, we hope you took away the following: 1) The execution of a passage of lines is much more difficult on the ground that it is on paper! 2) A successful forward passage of lines can set the conditions for a subsequent successful attack. 3) A successful rearward passage of lines can be instrumental in preserving combat forces for use later. 4) Coordination is critical in a passage of lines. With time available, the passing and stationary must meet and iron out the details. 5) A passage of lines can be an extremely chaotic operation. Effective communication between those involved can alleviate some of the chaos. 

NEXT MONTH

In our next article, we will focus on the extremely challenging operation of the relief in place. We will focus our article into basically the same sections as this past article. This will include discussion on why we conduct a relief in place, critical control measures needed in the relief, how to plan, prepare and execute the relief, and keys to success. Truly, the relief in place is one of the most difficult operations conducted on the battlefield. The combination of many moving pieces, the continuous threat of enemy indirect and direct fire, and an environment that is continually changing make this a challenge for any Commander and his unit.

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