Even with the participation of the UN forces in the war, South Korean forces failed to repel the North Korean forces' advance towards the south, so, on August 1, 1950, they retreated to the Nakdong River.
In August, 1950, communist nations and democratic nations had fierce combats at the Nakdong River battle line.
The Nakdong River defensive operation was a success in that the communists' threat to the democratic nations was eliminated.
Also, the UN forces' participation in the war boosted confidence of the troops and people of South Korea on ultimate war victory.