U.S. Army experiments dated back to 1944. They were dropped three years later after efforts to perfect a boot with sealed insulation failed to meet the test of long marches. The Navy had more promising results with the boot during the winter of 1948–1949 when Arctic clothing tests were conducted at Point Barrow, Alaska. Army and Navy tests at Mt. Washington, New Hampshire, the following winter were inconclusive. Marine Corps tests were held during the first four months of 1951 at the following places: MCEB, Quantico; Fort Churchill, Manitoba; Big Delta, Alaska; Pickel Meadows, California; and the Naval Medical Field Research Laboratory (NMFRL), Camp Lejeune.
“In addition to engineering tests,” states the Marine report, “the insulated rubber boots have been worn by test subjects selected from a variety of backgrounds; under conditions of activity varying from strenuous marching for 20 miles to complete immobility; in ambient temperatures from 58° to -42° F.; over terrain ranging from soft snow [to] hard snow, ice, sand, rocky ground, mud, gravel, water, and iced river banks; for periods of time corresponding to a normal working day and more than 72 hours. As now constructed, the insulated rubber boot, employing the vapor barrier principle, meets the requirements outlined previously and is satisfactory for use by Marine Corps ground troops in cold climate areas, supplanting the shoe-pac combination....”[345]
[345] LtCol G. W. Hardwick, “Summary of Marine Corps Experience with IRB [Insulated Rubber Boot], Rpt of 8 May 1951.” Other sources for the development of the boot, also found in G-4 files, Headquarters Marine Corps, are as follows: G. E. Folk, Abstract of Bowdoin College Rpt, Jun 1951, “The Penetration of Water into the Human Foot;” G-4 Rpt, “Resume of Activity re Insulated Rubber Boot,” 7 Feb 1952; G-4 Rpt, “Boot, Rubber, Insulated, Cold Weather,” 28 Nov 51; G-4 Rpt, “Fact Data Sheet, Boot, Insulated, Rubber,” n.d.; MajGen J. T. Selden memo to CMC, 26 Apr 52.
The distinguishing feature of the “thermal boot,” as it came to be popularly known, is an air space between the inner and outer layers of wool pile insulation, both of which are completely sealed off by latex from any contact with moisture. This air space, under pressure, produces a vapor barrier such that heat cannot readily escape when it is emitted from the foot. Thus the wearer of the boot supplies his own warmth, which is retained as long as he is active, regardless of prevailing temperatures. If, however, the walls of the air space are punctured and the insulation becomes wet, the moisture collected within the boot freezes at low temperatures if the wearer remains inactive. In such cases, severe frostbite may result.
Some of the tests were spectacular. One subject poured water containing pieces of ice into his boots and donned frozen socks before putting on the footgear. After 10 minutes of walking, the ice in the boots had turned to warm water, and there was no harmful effect on the man.
Another subject waded across a knee-deep creek at a temperature of zero. Before he had marched a mile in the snow, his feet had warmed the water in the boots, although his pants were frozen so stiff that he could scarcely walk.
Seldom has a military innovation been tested so thoroughly and scientifically in such a short time. Colonels Ion M. Bethel and John F. Stamm of Marine Corps Headquarters took a leading part in the development and procurement phases along with Lieutenant Colonel Gordon A. Hardwick. Major Vernon D. Boyd and Captain David R. McGrew, Jr. were active in the troop acceptance tests.
A good many “bugs” had to be eliminated before the boot met with complete Marine approval. The manufacturer’s modifications were effected with minimal delay.
It is perhaps needless to add that the thermal boot was not foolproof. Protection continued in subzero weather for at least an hour after the termination of activity, but it was inviting frostbite to remain motionless much longer. Socks had to be changed every 12 hours, and foot cleanliness and hygiene could not be neglected.
If a few such simple rules were observed, a man had virtually perfect frostbite protection in the coldest weather. In fact, it was seriously proposed that a Marine casualty of this sort should be charged with misconduct if he acquired his frostbite while provided with thermal boots and a change of socks.