For the other mushroom war, see Mushroom War (Earth).
The Mushroom War (1970–2019) was a war between the Mushrooms and the Koopas. Fighting occurred as early as 1970, but neither country officially declared war until 1985, when the expansionist Mushroom Kingdom directly attacked the friendly Koopa Kingdom. The Koopas attacked back, captured Princess Toadstool, and were near victory when Mario and Luigi arrived. The war spread to the rest of Plit around 1988, when Koopa spies uncovered a Mushroom plot to seize seven other kingdoms and Bowser responded by sending his children to their defense. Open hostilities lasted until 2015, when the Mushrooms and Koopas both joined the anti-form alliance during the Form Wars. The two kingdoms then signed a lasting peace treaty during the Poopocalypse.