A lot of things are kept undercover in undeclared wars.

Actually there was something close to an undeclared war going on.

The relationship has been peaceful (except for an undeclared naval war in 1798-99).

Tensions with France increased to the point that the period is described as an undeclared war.

Western analysts say that the two countries are "engaged in an undeclared cold war".

My roommate didn't have any use for the undeclared war in Vietnam.

But according to the briefing that was not the point of the undeclared war.

Though his spirit required combat, politics was now what provided him with an undeclared war.

The Japanese and other foreign countries are in an undeclared war with us.

This campaign was an undeclared war that lasted from 1938 to 1939.