Preceded by Operation Martlet to secure the right flank of the advance, Operation Epsom began early on 26 June, with units of the 15th (Scottish) Infantry Division advancing behind a rolling artillery barrage. Air cover was sporadic for much of the operation, because poor weather in England forced the last-minute cancellation of bomber support. Accompanied by the 31st Tank Brigade, the 15th (Scottish) Division made steady progress and by the end of the first day had overrun much of the German outpost line, although some difficulties remained in securing the flanks. In mutually-costly fighting over the following two days, a foothold was secured across the River Odon and efforts were made to expand this, by capturing tactically valuable points around the salient and moving up the 43rd (Wessex) Infantry Division. By 30 June, after German counter-attacks, some of the British forces across the river were withdrawn and the captured ground consolidated, bringing the operation to a close.