The U.S. Marine Corps made extensive use of the Sikorsky S55 (US Army H19 Chickasaw) in the Korean War. It was designated as the HRS in USMC service.
Marine Squadron HMR161 arrived in Korea on September 2, 1951 with 15 HRS1 helicopters.
Although HMR161 helicopters were operating in hot landing zones they did not lose any helicopters to enemy fire.
HRS1 helicopters were also used to relocate rocket launcher batteries. Because rockets create much visible dust when fired they make an easy target for enemy artillery. To reduce their exposure, launchers and crews were moved twice a day. Each HRS1 helicopter carried four rocket launchers and extra rockets as external cargo, with the crew in the cabin.
The HRS1 helicopter proved to be durable and reliable in Korean service.
https://en.wikipedia.org/wiki/Sikorsk...
footages from US National Archives