Explanation is one of the main aims of science. Scientists frequently seek to explain scientific phenomena. This paper addresses the relationship between scientific explanation and science denialism. In it, explanatory wars are introduced. An explanatory war is a situation in which the standard scientific explanation of a phenomenon is systematically denied by a group of people. It is argued that the mechanistic account of scientific explanation is helpful in order to face this kind of science denialism. Mechanistic explanations are resistant to the arguments usually raised by denialists. The relevant role of mechanistic explanations is illustrated by the case of tobacco disease denialism during the second half of twentieth century.