Yet lying about war is uniquely corrosive. When a president signals that the truth does not matter in wartime, he encourages his cabinet and his generals to mislead the country and one another about how the war is going. He creates a culture in which deadly mistakes and even war crimes can become more common. He makes it harder to win by hiding the realities of conflict and by making allies wary of joining the fight. Ultimately, he undermines American values and interests.