of the four main issues of contention during two years of negotiation. 605 sick, wounded, and/or injured UNC prisoners were exchanged for 6,030 sick or injured North Korean prisoners. Operation Big Switch, April–September 1953. Based on the success of the repatriations undertaken earlier, a general exchange of prisoners began in late April. During Operation Big Switch, prisoners were brought to Panmunjom, on the banks of the Sachong River. Each prisoner was then asked if he wished to cross the river and return to his countrymen or remain with his captors. Once the choice was made there was no turning back—hence the name Bridge of No Return. During this time 13,444 UNC prisoners returned to UNC countries, and 89,493 KPA and CPV prisoners returned to their countries. In March 1953, a further 25,000 KPA soldiers held in ROKA camps had been released into South Korea on President Syngman Rhee's orders in an attempt to wreck the armistice negotiations. Release of the crew of the USS Pueblo, December 23, 1968. On January 23, 1968, the USS Pueblo was captured by North Korean naval forces in international waters off the coast of North Korea. After being held prisoner for 11 months, the crew was released and allowed to walk across the bridge while a forced confession by the captain of the vessel was broadcast over loudspeakers. This action was the first in a series of events that escalated tensions between North Korea and the United States and its allies. Korean axe murder incident, August 18, 1976. This was the killing of two United States Army officers by North Korean soldiers in the Joint Security Area, near the Bridge of No Return, over the attempt to trim a poplar that obstructed vision between checkpoints, and heightened tensions on the border. This was followed by Operation Paul Bunyan, which ended in the felling of the tree by Task Force Vierra. Ceremonies on the bridge U.S. Army soldiers who are stationed at Camp Bonifas or Camp Liberty Bell in the Joint Security Area are offered the opportunity to have their promotion or reenlistment ceremonies held in the center of the Bridge of No Return. The bridge is split in half by the Military Demarcation Line which separates North Korean territory from South Korean territory. During a U.S. or ROK (Republic of Korea) ceremony, two guards are posted at the Demarcation Line facing west (toward North Korea).