Each of the first wave landing forces was divided into three echelons. The first echelon, carried across the Channel on barges, coasters and small motor launches, would consist of the main infantry assault force. The second echelon, carried across the Channel in larger transport vessels, would consist predominantly of artillery, armoured vehicles and other heavy equipment. The third echelon, carried across the channel on barges, would consist of the vehicles, horses, stores and personnel of the division-level support services. Loading of barges and transports with heavy equipment, vehicles and stores would start on S-tag minus nine (in Antwerp); and S minus eight in Dunkirk, with horses not loaded till S minus two. All troops would be loaded onto their barges from French or Belgian ports on S minus two or S minus one. The first echelon would land on the beaches on S-tag itself, preferably at daybreak around two hours after high tide. The barges used for the first echelon would be retrieved by tugs on the afternoon of S-tag, and those still in working order would be drawn up alongside the transport vessels to trans-ship the second echelon overnight, so that much of the second echelon and third echelon could land on S plus one, with the remainder on S plus two. The Navy intended that all four invasion fleets would return across the Channel on the night of S plus two, having been moored for three full days off the South coast of England. The Army had sought to have the third echelon cross in later separate convoys to avoid men and horses having to wait for as long as four days and nights in their barges, but the "Kriegsmarine" were insistent that they could only protect the four fleets from Royal Navy attack if all vessels crossed the Channel together.