Victory disease
Victory disease denotes when in military history, due to complacency or arrogance brought on by a victory or series of victories, an engagement ends disastrously for a commander and his forces.
A commander may disdain the enemy, and believe his own invincibility, leading his troops to disaster. That commander may employ strategies which, if effective in earlier combats or maneuvers, prove catastrophic against a new or smarter enemy; the commander afflicted by "victory disease" may also fail to anticipate a new enemy may use tactics different from those of old enemies. An overconfident commander may disregard military intelligence which would enable the commander to realize that new tactics are needed.
Though "victory disease" does not inevitably foretell defeat, it often precedes it. The term is also applied outside the military world.
Origin
The origin of the term ((戦勝病 senshoubyou) in Japanese is associated with the Japanese advance in the Pacific Theater of World War II, where, after attacking Pearl Harbor in 1941, Japan won a series of nearly uninterrupted victories against the Allies in Southeast Asia and the Pacific.