The strategy was utilized in the early 1950s by the hastily formed People's Volunteer Army during the Korean War, to garner support from the local Korean populace to win the war by driving the United Nations forces from the peninsula. At the battles of Chongchon river valley and Lake Changjin, the army employed guerrilla tactics in full scale, following the people's war doctrine. However, as they marched towards the South under Mao's stern orders after their decisive victories in northern Korea, they were met by an indifferent and sometimes hostile Southern population who, despite intimidation, were not willing to help them. This prevented them from defeating the UN forces in Korea and, after their hard-fought victory at the Third Battle of Seoul, they were beaten in the open by UN forces in the conclusion of their Third Phase Campaign. Later on the war turned into a stalemated two-year confrontation between the opposing forces. Thus, years after the war, the Chinese government began a series of army modernization and professionalization that would radically change the concept of the strategy, and in the 1980s and 1990s the concept of people's war was changed to include more high-technology weaponry.