the outbreak of the Bishops' Wars in Scotland in 1639, Ruthven offered his services to Charles I. He brought with him his two nephews, Major General John Ruthven and Colonel Frances Ruthven, both veterans of Swedish service. These joined a cohort of other Royalist Scots, including former colleague, Lieutenant General James King. During the 1639 campaign, he declined command of the Royalists in Scotland as he was not to be granted 'absolute authority' over them, instead being expected to defer to the nobility. His decision was wise and Edinburgh Castle soon easily fell to his former understudy, Alexander Leslie. After the Truce of Berwick was agreed, Ruthven was allowed to garrison the castle for the king and he defended it throughout 1640, becoming desperately ill after his provisions ran out. He and his English troops were allowed to leave the castle by negotiation. For his services he was raised to the Peerage of Scotland as Lord Ruthven of Ettrick in 1639 during the Bishops War and later created Earl of Forth in 1642. When the English Civil War broke out that year, Ruthven joined Charles at Shrewsbury with some 29 other Scottish veteran officers and after Henrietta Maria's intervention with the king. Ruthven commanded the Royalist forces at the Battle of Edgehill after the nominated commander, Robert Bertie, Earl of Lindsey, stepped down in a dispute over whether to arrange the army following the Dutch or the Swedish style. In the end the Swedish brigade system was chosen and Ruthven assumed command. Following the battle, Ruthven was appointed general-in-chief of the Royalist army. The Earl compelled the Earl of Essex to surrender Lostwithiel, and was wounded at both the first and second battles of Newbury. While some claim Ruthven's faculties had begun to decay, Ruthven had lost favour of his military inferior Prince Rupert, whose arrogance he detested. They fell out en route to face down the Army of the Solemn league and Covenant commanded by his friend Alexander Leslie. Believing Rupert inept, Ruthven returned to Oxford leaving Rupert in command. The prince lost the battle to Alexander Leslie and his English parliamentary allies on 2 July 1644. Ruthven thereafter served as Chamberlain to the Prince of Wales, having finally given up field service. Ruthven still maintained correspondence with Axel Oxenstierna, the regent and chancellor of Sweden. He visited Sweden on a mission for Charles II to raise military support