Well there certainly is a correlation between food availability and population expansion, which sometimes leads to an excessive population per land area that cannot be sustained, which can lead to territorial expansion, which can lead to war. But there are many factors that intervene in pro and con.
Taking Vietnam as an example: When Annam was confined to the periphery of the Red River Delta, there was the overthrow of the King, which led to an usurper on the throne, who in turn was overthrown by two warlord families, the Trinh and Nguyen, who cooperated for a century or so during which time the Trinhs ruled the Red River Delta heartland and the Nguyens found themselves confined to its southern edge with Champa at its back. Needing both land and population, they pushed down into Cham lands, where the relatively few valleys suitable for wet rice agriculture over time proved inadequate. The Nguyen offset this disadvantage for some years by developing Hoi An as a trading port. By 1698 they had reached the edges of today's Saigon, drawing them into Cambodian territory. As their Mekong Delta colony grew, they set up fleets to transport Mekong Delta rice into their home territories. As those populations expanded, they were able to keep sending settlers and armies south, fighting campaigns against the Thai and Lao states, intervening in Cambodian civil wars, and in one case going as far afield as Burma. But once their territorial gains exceeded their capacity to govern, discontent arose in the form of the Tay Son rebellion, which overthrew the Nguyens for a while, but left a Nguyen survivor in eventual control of the Mekong Delta. His defeat of both the Tay Son remnants and the Trinh, the reunification of the traditional Trinh and Nguyen territories, and consolidation of their Cham and Cambodian conquests, resulted in his accession to the throne as Gia Long in 1802.
If no one else paid attention to the population-food source balances in Indochina, the French General Staff certainly did. After their 1858 punitive expedition in partnership with Spain ended bottled up in Danang, Adm. Rigault sailed south to seize Saigon, cutting off the Imperial Army's rice supply lines and forcing its eventual capitulation, allowing the French to take over Cochinchina, and impose protectorates on Annam and its neighbors.
And in my humble opinion, Admiral Thierry de Argenlieu's 1946 declaration of the Republic of Cochinchina, made while Ho Chi Minh was enroute to France for the Fontainebleau conference to hammer out the details of French recognition of his government, was the first shot across the bow of the Indochina War. Without Cochinchina (Bien Hoa south to Camau) the DRVN territories would have been periodically short of rice and dependent upon imports in international markets. Something that HCM and the boys clearly understood even without their nationalist pretensions.
Brocheux and Hemery devote no few pages on the subject of 'balance of population and grain production' in Chapter 6 "The Impasses of Colonial Development" in their book: Indochina: An Ambiguous Colonization 1858-1954.
Phong trần mài một lưỡi gươm, Những loài giá áo túi cơm sá ǵ!