After many loses against North Korean, in 1950 the Republic of Korea (ROK), the United States and the United Kingdom forces set up a defense line on the Pusan Perimeter near the city of Pusan. After six weeks of conflict and continuous battles, the North Korean army had to retreat because of a shortage of its supplies. On the other hand, the U.N. and American forces used the Pusan port as a way to get supplies which was the key factor that led to their victory.