During the war, three British infantry divisions saw active service in Persia and Iraq, albeit only two were in the countries at the same time. There were heavy demands on British infantry formations during 1941 and 1942, with the first divisions released from the United Kingdom for service overseas, as the threat of invasion receded.

The first division to arrive in Iraq was the 50 (Northumbrian) Infantry Division. Its stay was short, as it arrived from Cyprus on 21 November 1941, and left on 13 January 1942 bound for Egypt.

The next to arrive was the 5 Infantry Division, which landed from India on 28 August 1942. It came under command of III Corps.

The 56 (London) Infantry Division was sent out from the United Kingdom arriving on 4 November 1942. This division came under command of XXI Indian Corps.

Late 1942 was the period of greatest threat of invasion of Iraq and Persia by German forces through the Caucasus mountains, as their advance through the U.S.S.R. continued. As this threat receded, the British divisions were transferred. Both moved to Egypt, with the 5 Infantry Division leaving on 31 January 1943 to join XIII Corps in Egypt, in order to prepare for the invasion of Sicily. The 56 (London) Infantry Division left on 19 March 1943, to travel through Egypt onto Tunisia, where it joined X Corps. This constituted one of the most remarkable journeys by any formation during the Second World War, a total of 3,200 miles by road, in just over four weeks.