The British had anticipated a Japanese attack, but lacked the resources to defend the area because of their engagement in the war in Europe. The troops from the Punjab Regiment filled in the Seria oilfield oilwells with concrete in September 1941 to deny the Japanese their use. The remaining equipment and installations were destroyed when the Japanese invaded Malaya. By the end of the war, 16 wells at Miri and Seria had been restarted, with production reaching about half the pre-war level. Coal production at Muara was also recommenced, but with little success.