Today, 54 years ago, on March 24, 1971 (February 28, 1971), South Vietnam's attempt to invade Laos was declared a failure. On March 24, 1971, under the resistance of the Communist Army, South Vietnam was forced to terminate its military operation to cut off the enemy's supply line in Laos in advance. South Vietnamese forces entered Laos with the support of U.S. Air Force and artillery, and 44 days later announced their withdrawal. The military operation was aimed at destroying the communist supply line known as Ho Chi Minh Avenue. During the most intense battle, South Vietnamese troops in Laos reached 20,000. South Vietnamese troops were severely injured: 1146 soldiers were killed. The United States lost 89 helicopters and 51 American soldiers were killed.