Operation Compass was the first big Allied military operation of the Western Desert Campaign during World War II. British and other Commonwealth forces attacked Italian forces in western Egypt and eastern Libya in December 1940, with great success. The Western Desert Force (Lieutenant-General Sir Richard O'Connor) with about 30,000 men, advanced from Mersa Matruh in Egypt on a five-day raid on the Italian positions of the 10th Army (Marshal Rodolfo Graziani), which had about 150,000 men in fortified posts around Sidi Barrani and in eastern Libya (Cyrenaica).The 10th Army was swiftly defeated and the British prolonged the operation, to pursue the remnants of the 10th Army to Beda Fomm and El Agheila on the Gulf of Sirte. The British lost 1,900 killed and wounded, about 10 percent of their infantry and took 138,000 Italian and Libyan prisoners, hundreds of tanks and over 1,000 guns and aircraft. The British were unable to continue beyond El Agheila, due to broken-down and worn out vehicles and the diversion of the best-equipped units to the Greek Campaign.