Wolseley then decided to approach Cairo from a different route. He resolved to attack from the direction of the Suez canal. 'Urabi knew that Wolseley's only other approach to Cairo was from the canal, and he wanted to block it. Ferdinand de Lesseps, upon knowing of Urabi's intentions, assured him the British would never risk damaging the canal, and would avoid involving it in operations at all costs according to Lutsky, he even "gave his word of honour to Urabi not to permit the landing of British troops in the Canal Zone, and Urabi trusted de Lesseps. By so doing, Urabi committed a grave military and political mistake". 'Urabi listened to his advice and did not block the canal, leaving it open for an invasion by British forces. When Wolseley had arrived at Alexandria on 15 August he immediately began to organise the movement of troops through the Suez Canal to Ismaïlia. This was accomplished so quickly, Ismailia was occupied on 20 August without resistance. Ismailia was quickly reinforced with 9,000 troops, with the engineers put to work repairing the railway line from Suez. A small force was pushed along the Sweet Water Canal to the Kassassin lock arriving on 26 August. Egyptian attack at Kassassin 'Urabi attempted to repel the advance and attacked the British forces near Kassassin on 28 August. The British troops were caught by surprise, as they did not expect an attack. Fighting was intense but the two British battalions, with their 4 artillery pieces, held their position. The British Heavy Cavalry, composed of the Household Cavalry and the 7th Dragoon Guards had been following the infantry and were encamped away. When the cavalry arrived, the British went onto the offensive and causing heavy casualties on the Egyptians, forced them to retreat . A further attack by Egyptian forces at Kassassin was repulsed and the Egyptians retired to their lines to build defences. Capture of Mahmoud Fehmy At around the same time as the first battle at Kassassin, the British scored a major success with the capture of the Egyptian chief military engineer, General Mahmoud Fehmy. The exact circumstances of his capture are unclear - according to one account, he had changed into civilian clothes due to the heat, and had gone for a walk accompanied by only one other officer when he was ambushed by a group of British cavalrymen. The loss of Fehmy was