Operation Strangle was a sustained interdiction attack on North Korea's supplies and communications by the United Nations forces during the Korean War.
The North Koreans countered the campaign by moving anti-aircraft (AA) guns and crews towards the front line and placing them in higher concentrations around important targets, causing heavy casualties in the UN forces.
[1] By December 1951, North Korea was able to repair rail cuts in less than six hours, bridges in two to four days, and other bomb damages fairly quickly.
The USAF created an “air pressure strategy” to put political pressure on the North Korean politicians, and the U.S. Air Force (USAF) continued an aerial bombing campaign throughout the negotiations, until July 27, 1953 when armistice negotiations came to a halt over prisoners of war (POWs).
[4] Operation Strangle led the U.N. forces to hit a range of weapons, including AA guns and strategic positions.