Evaluation of transport helicopter techniques continued during the period despite ever-present minor difficulties. At least one new HMR-161 tactical maneuver was scheduled each month to evaluate existing procedures and determine full operational capabilities of the aircraft. During these landing exercises both the infantry and helicopter commanders and their staffs had the opportunity to further develop vertical envelopment techniques that would soon be the new trademark of U.S. Marine Corps operations. Most of the time HMR-161 operations drew more attention than those of VMO-6, but pilots in the latter unit had a host of division Marines who could attest to the skills and critical role performed by helicopter fliers in the composite observation squadron. VMO-6 had pioneered the night casualty evacuation service, and during the active fighting in Korea, had flown out more than 1,000 Marines from frontline medical facilities to better-equipped ones in the rear areas. These flights were made in all kinds of weather and without the benefit of adequate instrumentation or a homing device. No other Eighth Army helicopter unit made regularly scheduled night frontline evacuations.[319] [319] A relatively small number of night med evac flights was also being flown by HMR-161. During March 1953, for example, in transferring 283 casualties to the hospital ships, squadron helicopters made only 15 flights at night. The courage of these VMO-6 pilots was recalled nearly 15 years later by a former executive officer of the 1st Marines: The flying of the evacuation helicopters from the jury-rigged and inadequate landing sites was nothing short of miraculous. I’ve always contended those pilots of the observation squadron received far less credit than they deserved. They used to fly at night, to frontline landing strips, where I had difficulty walking without barking my shins.[320] [320] Col Glenn R. Long ltr to Hd, HistBr, G-3 Div, HQMC, dtd 11 Jun 67.