The Suez Canal at War

In 1882 Liberal politician Sir Charles Dilke expressed the essential importance of the Suez Canal to the British Empire: 

As regards the Suez Canal, England has a double interest: it has a predominant commercial interest, because 82 percent of the trade passing through the Canal is British trade, and it has a predominant political interest caused by the fact that the Canal is the principal highway to India, Ceylon, the Straits [of Malacca], and British Burma, where 250 million people live under our rule, and also to China, where we have vast interests and 84 per cent of the external trade of that still more enormous Empire.

Turkish forces launched their first attack on the Suez Canal, Britain's vital link to the East and Australia, on 3 February 1915, having dragged heavy loads of pontoons and other bridging equipment over 160 km of desert. The attack was poorly coordinated and easily repulsed, and the Turkish forces were driven back into the Sinai desert. After this attack the British forces pushed their defenses out 10 km east of the canal. 

Turkish Troops En Route to the Suez Canal

The Gallipoli campaign subsequently limited the resources available for the defense of the Canal but also deprived the Turks of the ability to mount a renewed offensive. The end of the Gallipoli campaign in December 1915 dramatically altered the military situation on the Sinai peninsula. Turkey now had the troops available to launch a new drive on the Canal, and the British sufficient troops to attempt to defend it in depth. That effort to gain control of the Canal was defeated strategically at the Battle of Romani fought in the northern Sinai Desert in August 1916.

From The Australian War Memorial Website and Over the Top magazine