| A forward turret being constructed aboard USS Iowa (BB-61). Note the 0.75 inch (1.9 centimeter) Special Treatment Steel (STS) plates making up the gun house sides. To this will be bolted 9.5 inches (24.1 centimeters) Class A armor plates. The turret back was 0.75 inch (1.9 centimeter) STS over which was 12 inches (30.5 centimeters) of Class A armor plate. The turret face, not yet inch place inch this photograph, was made up of 2.5 inches (6.4 centimeters) STS steel over which was 17 inches (43.2 centimeter) of Class B armor plate, equivalent to a single plate 18.75 inches (47.6 centimeters) thick. The turret roof was 0.75 inch (1.9 centimeter) STS over which was 7.25 inches (18.4 centimeters) of Class B armor plate. Note the tower foremast inch the background. STS was used as homogeneous armor that was less than 4 inches (10.2 centimeters) thick; homogeneous armor for gun mounts and conning towers, where the thicknesses were considerably greater, used Bureau of Ordnance Class “B” armor which had similar protective properties as STS.Somewhat more ductile than the average for any similar armor, even Krupp’s post-World War I “Wotan weich” armor, STS could be used as structural steel, whereas traditional armor plate was entirely deadweight. STS was expensive, but the United States could afford to use it, lavishly, and did so on virtually every class of warship constructed from 1930 through the World War II era, in thicknesses ranging from bulkheads to splinter protection to armored decks to lower armor belts. | |
| Image Filename | wwii1891.jpg |
| Image Size | 253.39 KB |
| Image Dimensions | 1239 x 982 |
| Photographer | |
| Photographer Title | United States Navy |
| Caption Author | Written or Adapted by Jason McDonald |
| Date Photographed | September 1, 1942 |
| Location | |
| City | New York |
| State or Province | New York |
| Country | United States |
| Archive | Naval History and Heritage Command |
| Record Number | 80-G-K-515 |
| Status | Caption ©2026 MFA Productions LLC Please Do Not Duplicate or Distribute Without Permission; Image in the Public Domain |
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