<P> Many concerns were raised over Charles's marriage to a Roman Catholic, French princess Henrietta Maria, in 1625 . The Parliament refused to assign him the traditional right to collect customs duties for his entire reign, deciding instead to grant it only on a provisional basis and negotiate with him . </P> <P> Charles, meanwhile, decided to send an expeditionary force to relieve the French Huguenots whom French royal troops held besieged in La Rochelle . Military support for Protestants on the Continent was, in itself, popular both in Parliament and with the Protestant majority in general, and it had the potential to alleviate concerns brought about by the King's marriage to a Catholic . However, Charles's insistence on having his unpopular royal favourite George Villiers, the Duke of Buckingham, assume command of the English force undermined that support . Unfortunately for Charles and Buckingham, the relief expedition proved a fiasco (1627), and Parliament, already hostile to Buckingham for his monopoly on royal patronage, opened impeachment proceedings against him . Charles responded by dissolving Parliament . This move, while saving Buckingham, reinforced the impression that Charles wanted to avoid Parliamentary scrutiny of his ministers . </P> <P> Having dissolved Parliament and unable to raise money without it, the king assembled a new one in 1628 . (The elected members included Oliver Cromwell and Edward Coke .) The new Parliament drew up the Petition of Right, and Charles accepted it as a concession in order to obtain his subsidy . Amongst other things, the Petition referred to the Magna Carta . However, it did not grant him the right of tonnage and poundage, which Charles had been collecting without Parliamentary authorisation since 1625 . Several of the more active members of the opposition were imprisoned, which caused some outrage; one, John Eliot, subsequently died in prison, becoming regarded as a martyr for the rights of Parliament . </P> <P> Charles I avoided calling a Parliament for the next decade, a period known as the "personal rule of Charles I", or the "Eleven Years' Tyranny". During this period, Charles's lack of money determined policies . First and foremost, to avoid Parliament, the King needed to avoid war . Charles made peace with France and Spain, effectively ending England's involvement in the Thirty Years' War . However, that in itself was far from enough to balance the Crown's finances . </P>

Which was a cause of the thirty years' war (points 3)