Operation Compass was the first large Allied military operation of the Western Desert Campaign (1940–1943) during World War II. British and other Commonwealth forces attacked Italian forces in western Egypt and Cyrenaica, the eastern province of Libya, from December 1940 to February 1941, with great success. The Western Desert Force (Lieutenant-General Richard O'Connor) with about 30,000 men, advanced from Mersa Matruh in Egypt on a five-day raid against the Italian positions of the 10th Army (Marshal Rodolfo Graziani), which had about 150,000 men in fortified posts around Sidi Barrani and in Cyrenaica.