The United States' S-class submarines, often simply called S-boats (sometimes "Sugar" boats, after the then-contemporary Navy phonetic alphabet for "S"), were the first class of submarines with a significant number built to United States Navy designs. They made up the bulk of the USN submarine service in the interwar years and could be found in every theater of operations. While not considered "Fleet Submarines" in the traditional sense of that term, they were the first submarines in the USN designed for open ocean, blue water operations. All previous submarines had been intended for harbor or coastal defense. These boats were intended to have greater speed and range than previous classes, with improved habitability and greater armament.
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