They do use GPS for military navigation, but as part of a broader suite of systems. For example, Tomahawk missiles use INS for continuous estimates, plus a comb

They do use GPS for military navigation, but as part of a broader suite of systems. For example, Tomahawk missiles use INS for continuous estimates, plus a combination of visual and radar terrain contour matching and GPS to correct the inertial fix. And probably a few other things they don't talk about publicly. When they can get it, GPS reduces error, though I agree that systems are designed to be tolerant of jamming and shootdowns.