 Italy declared war on the United Kingdom on 10 June 1940 . Bordering on the Italian colony of Libya was the Kingdom of Egypt . Although a neutral country , Egypt was occupied by the British under the terms of the Anglo @-@ Egyptian Treaty of 1936 , which allowed British military forces to occupy Egypt if the Suez Canal was threatened . A series of cross @-@ border raids and skirmishes began on the frontier between Libya and Egypt . On 13 September 1940 , an Italian force advanced across the frontier into Egypt , reaching Sidi Barrani on 16 September , where the advance was halted until logistical difficulties could be overcome . 
