After the Korean Peninsula was partitioned into North and South following its liberation in 1945 from Japanese occupation, Western culture was introduced into South Korea on a small scale, with a few Western-styled bars and clubs playing Western music. After the Korean War (1950–53) U.S. troops remained in South Korea, causing American and world culture to spread in South Korea and Western music to gradually become more accepted. Prominent figures of American entertainment like Nat King Cole, Marilyn Monroe and Louis Armstrong held USO shows in South Korea for the U.S. Army. These visits prompted attention from the Korean public. In 1957, the American Forces Korea Network radio started its broadcast, spreading the popularity of Western music. American music started influencing Korean music, as pentatony was gradually replaced by heptachords and popular songs started to be modeled after American ones.