System for modern military?

[LibraryOgre]

I would suggest Savage Worlds. Weird Wars I and Weird Wars II really getting into it, but the Core Book has more than enough gear and vehicles.

Savage Worlds has both rules for tactical combat and abstracting things via Chases, Quick Encounters, Dramatic Tasks and Mass Battle Rules.

I would, as well. While it's "generic", I think it handles modern combat without a ton of crunch, and you can simulate specialties through Edges and Hindrances.