From the outbreak of the Korean War following the invasion of South Korea by North Korea on 25 June 1950, the KPA, had enjoyed superiority in both manpower and ground combat equipment over the ROK and UN forces dispatched to South Korea to prevent it from collapsing. The North Korean strategy was to aggressively pursue UN and ROK forces on all avenues of approach south and to engage them, attacking from the front and initiating a double envelopment of both flanks of the defending units, which allowed the KPA to surround and cut off the opposing force, forcing it to retreat in disarray. From their initial 25 June offensive to fighting in July and early August, the KPA used this tactic to defeat the UN forces they encountered and push it south. However, with the establishment of the Pusan Perimeter in August, UN forces held a continuous line which the KPA could not flank. The KPA advantages in numbers decreased daily as the superior UN logistical system brought in more troops and supplies to the UN forces.