I think a two-pronged (at least) approach to national defense is needed. Obviously you need an army.

But then you need to make an equal (or larger) commitment to activities that promote peace. That includes a lot of things: disarmament, easing of tensions between countries, repudiating international economic factors that trigger hostilities.

In the case of the US border with Mexico, for example, the immediate problem is people wanting to escape bad economic and social conditions in Mexico. But a good deal of those bad economic conditions are the result of US policies regarding petroleum and subsidized farming and illegal weapons exports and drug imports. How can a small farmer in Mexico hope to compete with a gigantic government-subsidized industrial farm in Iowa, especially when every day he runs the risk of an encounter with a heavily-armed drug gang?

Admittedly, though, it is sort of hard to see what the west could have done to be more cooperative with Russia...