North Korean troops, hampered by supply shortages and massive losses, continually staged attacks on UN forces in an attempt to penetrate the perimeter and collapse the line. The UN forces, however, used the port to amass an overwhelming advantage in troops, equipment, and logistics, and its navy and air forces remained unchallenged by the KPA during the fight. After six weeks, the KPA force collapsed and retreated in defeat after the UN force launched a counterattack at Inchon on September 15 and the UN forces in the perimeter broke out from the perimeter the following day. The battle would be the furthest the KPA would advance in the war, as subsequent fighting ground the war into a stalemate.