Percival was ultimately responsible for the men who served under him, and with other officers – notably Major-General David Murray-Lyon, commander of the Indian 11th Infantry Division – he had shown a willingness to replace them when he felt their performance was not up to scratch. Perhaps his greatest mistake was to resist the building of fixed defences in either Johore or the north shore of Singapore, dismissing them in the face of repeated requests to start construction from his Chief Engineer, Brigadier Ivan Simson, with the comment "Defences are bad for morale – for both troops and civilians".