Dirty wars. When "War" is capitalized the phrase "Dirty War" refers to the Argentine Dirty War. See this discussion. Otherwise, the phrase "dirty wars" refers to this dictionary definition:
From a dictionary search on Google:
Dirty War Index: a tool used to predict the possible outcome of a military war method(n) dirty war (an offensive conducted by secret police or the military of a regime against revolutionary and terrorist insurgents and marked by the use of kidnapping and torture and murder with civilians often being the victims) "thousands of people disappeared and were killed during Argentina's dirty war in the late 1970s"