Final answer:
Great Britain's primary concern during the creation of Iraq's borders post-WWI was securing control over the region's oil resources, ensuring protection of strategic routes like the Suez Canal, and maintaining the stability of oil-rich countries to preserve British economic and strategic interests.
Step-by-step explanation:
The largest consideration for Great Britain during the creation of Iraq's borders after World War I was the control and access to oil resources in the Middle East.
After the war, Great Britain and France divided the former Ottoman territories into nations, with little regard for the ethnic or tribal divisions that existed. Britain, motivated by its imperial interests, moved to ensure control over oil fields and sought to protect routes, such as the Suez Canal, vital to their naval and merchant marine operations.
The creation of Iraq's borders and the establishment of a British mandate over the region were influenced by the discoveries of oil and the anticipation of its future importance.
Great Britain established geometric boundaries for these new states, and used its influence to create a regime in Iraq that was favorable to British interests. Specifically, the British-controlled multinational, TPC, received a lengthy concession to develop Iraq's oil, underscoring the centrality of oil in Britain's considerations.
Further, Britain had to balance its commitments to Arab leaders, who had supported them during the war, against other agreements such as the Balfour Declaration and the promises made to the Arab peoples, leading to complex political maneuvering.
Nonetheless, Britain's overriding concern was to secure the stability of oil-rich countries and maintain its own economic and strategic interests in the region.