The other major European conflict of the period was the 1568 to 1648 Eighty Years' War between Spain and the Dutch Republic, suspended in 1609 by the Twelve Years' Truce. The Spanish strongly objected to its commercial provisions and when Philip IV became king in 1621, he resumed the war. The cost proved extremely high, increased after 1628 by a proxy war with France over the Mantuan succession. While the Spanish Empire reached its maximum extent under Philip's rule, its complexity and size made it increasingly difficult to govern, or enact essential reforms.