Heavy U.S. air attacks that began with an order by President Richard Nixon on May 8 are widened to include more industrial and non-military sites. In 190 strikes, the United States lost one plane but shot down four. The new strikes were part of the ongoing Operation Linebacker, an effort launched in response to the massive North Vietnamese invasion of South Vietnam on March 30. The purpose of the raids were to interdict supplies from outside sources and the movement of equipment and supplies to the North Vietnamese troops in South Vietnam. The strikes concentrated on rail lines around Hanoi and Haiphong, bridges, pipelines, power plants, troops and troop training facilities, and rail lines to China.