In November 1943 US Marines sustained high casualties when they overwhelmed the 4,500-strong garrison at Tarawa. This helped the Allies to improve the techniques of amphibious landings, learning from their mistakes and implementing changes such as thorough pre-emptive bombings and bombardment, more careful planning regarding tides and landing craft schedules, and better overall coordination. Operations on the Gilberts were followed in late-January and mid-February 1944 by further, less costly, landings on the Marshall Islands.