Great Britain began the first phase of the North African campaign shortly after Italy declared war on June 10, 1940. General Archibald Wavell, commander in chief of British forces in the Middle East, felt it necessary to prove to Mussolini that the Allies were not about to let any Axis aggression go unchecked. Wavell sent a couple of armored vehicles from British-controlled Egypt to the Italian colony of Cyrenaica in Libya. After smashing through the barbed wire fence erected by the Italians, the British force paraded around two Italian forts, then crossed the border back into Egypt. The action was the beginning of a fight that would go on almost to the end of the war.
Mussolini showed little concern for the British presence in Egypt. His forces in the region greatly outnumbered those of the British, and he believed that the British posed little threat to what he saw as the start of the new Roman Empire.
On August 4, Mussolini ordered his forces to invade British Somaliland, southeast of Egypt. The British, greatly outnumbered, quickly withdrew from the territory, and on August 17 the Italian forces took the colony's capital, Berbera. The move had dire potential consequences for the British; if the United States, still neutral at the time, were to declare the Red Sea unsafe because of the Italian presence, it could cut off an important British supply line.
While Great Britain bolstered its forces and tried to formulate a military response to the Italian invasion of Somaliland, Mussolini, having learned from Hitler that an invasion of England was imminent, encouraged Marshal d'Armata Rodolfo Graziani, commander in chief of Italian forces in North Africa, to press Italy's advantage by invading Egypt. When Germany was forced to cancel Operation Sea Lion — the invasion of England — Graziani was reluctant to move, but he finally did so at Mussolini's urging on September 13. Five divisions crossed the border and, despite British resistance, successfully advanced about sixty-five miles to the coastal town of Sidi Marrani, where a strong defensive perimeter had been established.
Wavell was not about to let the Italians take Egypt, and on December 9, a British Western Desert Force of 30,000 attacked the Italian stronghold, taking the Italians by surprise and capturing 20,000 prisoners. Flushed with an easy victory, Lieutenant General Richard O'Connor, commander of the British force, decided to press on into Libya. He very quickly took the border town of Bardia, then proceeded forward, capturing nearly every town his force encountered. In just ten weeks, O'Connor's army, which was greatly outnumbered in the region, crossed 500 miles, captured the province of Cyrenaica, and took an amazing 130,000 prisoners.
O'Connor felt unstoppable and was eager to advance on the Libyan capital of Tripoli, but Wavell said no. His orders were to supply fresh troops to Greece, so he cut the Libyan force in the hope that the smaller army would still be able to control Cyrenaica.