you don't have a military

The only leftist ideology that advocates against an active military is anarchism. Anarchists prefer spontaneous militias that activate as soon as another state acts on them. Obviously there are downsides to this practice as 1) gathering up a militia and organizing them can take time away from defending against outside oppressors, which can jeopardize defense in general, and 2) gathering up a militia of normal folk in a society means they won't be actively trained in conducting warfare effectively, or at least not as much as another state that does have an active military - this also represents a lower hand which can again jeopardize defense in general.

Marxist-Leninist communists believe that an active military that trains its population and performs drills regularly is the most suitable defense against capitalist states, since they have their own military doing the same.