| Subclass U | Military science (General) |
| Subclass UA | Armies: Organization, distribution, military situation |
| Subclass UB | Military administration |
| Subclass UC | Maintenance and transportation |
| Subclass UD | Infantry |
| Subclass UE | Cavalry. Armor |
| Subclass UF | Artillery |
| Subclass UG | Military engineering. Air forces |
| Subclass UH | Other services |
https://www.loc.gov/aba/cataloging/classification/lcco/lcco_u.pdf