At the beginning of World War II,
United States destroyers were organized into squadrons, even-numbered in the Atlantic; odd-numbered in the Pacific. Listings are given as follows:
- Unconverted flush deckers were assigned to squadrons 27 and 29–33.
- Except for the three highest-numbered Sims-class 1570-tonners assigned as squadron leaders, new-construction 1,500-tonners, 1,570-tonners and 1,850-ton leaders from the 1930s were assigned to squadrons 1, 2, 3, 4, 5, 6, 8 and 9.
- 1,620-ton Benson- and 1,630-ton Gleaves-class ships were assigned to squadrons 7 and 10–19 as they entered service.
- 2,100-ton Fletcher-class ships were assigned squadron numbers 21–25 and 45–58.
- 2,200-ton short hull (Allen M. Sumner-class) and long hull (Gearing-class) destroyers were assigned to squadrons 60 and higher plus the late-war re-establishment of DesRon 10.