The Duke of Buckingham (1592–1628), who increasingly was the actual ruler of Britain, wanted an alliance with Spain. Buckingham took Charles with him to Spain to woo the Infanta in 1623. However, Spain's terms were that James must drop Britain's anti-Catholic intolerance or no marriage. Buckingham and Charles were humiliated and Buckingham became the leader of the widespread British demand for a war against Spain. Meanwhile, the Protestant princes looked to Britain, since it was the strongest of all the Protestant countries, to give military support for their cause. His son-in-law and daughter became king and queen of Bohemia, which outraged Vienna. The Thirty Years' War began in 1618, as the Habsburg Emperor ousted the new king and queen of Bohemia, and massacred their followers. Catholic Bavaria then invaded the Palatine, and James's son-in-law begged for James's military intervention. James finally realized his policies had backfired and refused these pleas. He successfully kept Britain out of the European-wide war that proved so heavily devastating for three decades. James's backup plan was to marry his son Charles to a French Catholic princess, who would bring a handsome dowry. Parliament and the British people were strongly opposed to any Catholic marriage, were demanding immediate war with Spain, and strongly favored with the Protestant cause in Europe. James had alienated both elite and popular opinion in Britain, and Parliament was cutting back its financing. Historians credit James for pulling back from a major war at the last minute, and keeping Britain in peace.