The War of Spanish Succession
Charles II died without an heir, leaving Spain to his sisters, one married to Leopold Habsburg, the other to Louis Bourbon. Balance of power principles called for a division of the spoils, but Charles' will called for the inheritance to be kept intact, going to Louis XIV's grandson. France and Spain would have been united, thus breaking the balance of power. The Grand Alliance didn't want this (England, Austria, Prussia, Holland). So they fought.
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