Charles attempted to arrest five members of Parliament (the Five Members) on January 4, 1642 during the English Civil War. When that plan backfired because the members had been tipped off ahead of time, on 10 Jan he left London with his household for Hampton Court, accompanied by a troop of approximately three hundred armed men commanded by his nephew Prince Rupert.[82] Charles began building his forces, establishing his court first at York and later at Oxford on 29 October after failing at the Siege of Gloucester,[83] and the King formally declared war after issuing pamphlets declaring Parliament to be in rebellion.[84] Both sides started raising armies,[85] leading to an eventual standoff between Royalists and Parliamentarians.