Text: They trotted out numerous theories to establish the Kosovo mission's  Air power alone had never won a war, the Serbs had proven their invincibility against Hitler, and negotiation backed by gradual military escalation had failed in Vietnam.
Entailment: According to them the Serbs had proved themselves invincible in the face of Hitler's forces.
Contradiction: The Americans won the war in Vietnam after using negotiation with military escalation.