The Middle East Theatre of World War II is defined largely by reference to the British Middle East Command, which controlled Allied forces in both Southwest Asia and eastern North Africa. From 1943, most of the action and forces concerned were in the adjoining Mediterranean Theatre.
The region was quiet for the first few months of the war, until Fascist Italy declared war against France and Britain on June 10, 1940. It remained a major active theatre for two and a half years until the British Commonwealth Eighth Army crossed the border from Libya into Tunisia. In February 1943, command of the Eighth Army passed from the Middle East Command to the Allied Joint command for the Mediterranean, AFHQ. The Middle East Theatre remained quiet for the remainder of the war.
The Allies initially believed that the Middle East (Southwest Asia) could become a major operational theatre, because they thought that the Germans might invade the area. This did not materialise, although when Allied forces occupied much of the area, in anticipation of such an invasion, there was fighting against Vichy French forces in Lebanon and Syria, and against Iraq in the Anglo-Iraqi War.
The Italian forces in North Africa greatly outnumbered the Allies. However, Allied forces were able to not only defend against Italian attacks but also to defeat the Italians and occupy their colonies in Ethiopia and Somaliland. By February 1941, Commonwealth forces appeared to be on the verge of overrunning the last Italian forces in Libya, which would have ended Axis control in all of Africa.
While the fighting was taking place in Libya, Axis forces were attacking Greece. The Allied commander, General Archibald Wavell, was ordered to STOP his advance against Libya and sent troops to Greece. He disagreed with this decision but followed his orders.
The Allies were unable to stop Greece falling to the Axis forces and before they could retake the initiative in the Western Desert the German Afrika Korps had entered the theatre. It would not be until early in 1943, after another year and a half of hard fighting and mixed fortunes, that the Axis forces would be finally driven out of Libya and the theatre would again become a backwater.