Egyptian volunteers were serving in the Egyptian Army, deployed mainly in the Sudan with three battalions in the EEF, along with 98,000 labourers, 23,000 of whom were serving overseas. The number of Egyptian enlistments could not be increased as conscription could threaten the production of much needed food and cotton and the stability of Egypt. Also by this time, much of the railway lines in Egypt that were not crucial to the production of cotton, sugar, cereals and forages, had already been lifted and used on the military railway, except the Khedivial Railway from Alexandria to Dabaa which was available for emergencies. The Egyptian Labour Corps and the Egyptian Camel Transport Corps had performed invaluable service during the Sinai campaign and would perform even greater service and hardships during the coming Palestine campaign. As the war dragged on and the fighting moved beyond the Egyptian border, many Egyptians felt the war no longer concerned them. At the same time the increasing need for Egyptian personnel turned volunteers into forced labour, although "highly paid," in a system controlled by the local mudirs. Defence of the Suez Canal (1915–16) From 26 January to 4 February 1915 the Suez Canal was attacked by a large force of the Ottoman Army. Beginning on 26 and 27 January, two smaller flanking columns of the Ottoman Army made secondary attacks near Kantara in the northern sector of the Canal and near Suez in the south. These were followed by the main attacks on 3 and 4 February, on the Suez Canal to east of the Suez to Kantara Railway. Kress von Kressenstein's Ottoman Suez Expeditionary Force advanced from Southern Palestine to arrive on the Canal on 2 February when they succeeded in crossing the Canal near Ismailia on the morning of 3 February 1915. Only two Ottoman companies successfully crossed the canal, the rest of the advance party abandoning attempts to cross as a result of the strong British defence by 30,000 men of the Imperial Service Cavalry Brigade and the Bikaner Camel Corps supported by Egyptian Army and Indian mountain artillery. The British then amassed troops at the scene which made another crossing impossible. The Ottoman companies held their positions until the evening of 3 February 1915, when the commanding officer ordered them to withdraw. The retreat proceeded "orderly, first into a camp ten km east of Ismailia". Subsequently, Ottoman advance troops and outposts were