Both Mary, Queen of Scots, and Lord Darnley had strong claims on the English throne through their mutual grandmother Margaret Tudor. This eventually led to the accession of the couple's only child James as King of Scotland, England, and Ireland in 1603. However, this was a Personal Union, as the three Kingdoms shared a monarch, but had separate governments, churches, and institutions. Indeed, the personal union did not prevent an armed conflict, known as the Bishops' Wars, breaking out between England and Scotland in 1639. This was to become part of the cycle of political and military conflict that marked the reign of Charles I of England, Scotland and Ireland, culminating in a series of conflicts known as the War of the Three Kingdoms. The trial and execution of Charles I by the English Parliament in 1649 began 11 years of republican government known as the English Interregnum. Scotland initially recognised the late King's son, also called Charles, as their monarch, before being subjugated and forced to enter Cromwell's Commonwealth by General Monck's occupying army. During this period, the principal members of the House of Stuart lived in exile in mainland Europe. The younger Charles returned to Britain to assume his three thrones in 1660 as "Charles II of England, Scotland and Ireland", but dated his reign from his father's death eleven years before.