The landing on Omaha Beach was the hardest fought and most costly of the D-Day landings, and the one that came closest to failure. A combination of a strong defensive position, rough seas, the loss of most of the supporting tanks and artillery, a too-short naval bombardment and an ineffective aerial bombardment saw the first wave of American troops pinned down on the water's edge, and although by the end of the day the landing was secure the Omaha beachhead was still less than a mile deep.