Answer
The Treaty of the Pyrenees, signed in 1659, significantly impacted Philip IV's reign. It ended the Franco-Spanish War, which had lasted for over 20 years. The treaty ceded several territories to France, including Roussillon and Artois, and recognized French control over Alsace. It also arranged the marriage of Philip IV's daughter, Maria Theresa, to Louis XIV of France, a move intended to strengthen ties between the two countries.