Why was the execution of Charles I a milestone in English history?

n London, King Charles I is beheaded for treason on January 30, 1649.

Charles ascended to the English throne in 1625 following the death of his father, King James I. In the first year of his reign, Charles offended his Protestant subjects by marrying Henrietta Maria, a Catholic French princess. He later responded to political opposition to his rule by dissolving Parliament on several occasions and in 1629 decided to rule entirely without Parliament. In 1642, the bitter struggle between king and Parliament for supremacy led to the outbreak of the first English civil war.

The Parliamentarians were led by Oliver Cromwell, whose formidable Ironsides force won an important victory against the king’s Royalist forces at Marston Moor in 1644 and at Naseby in 1645. As a leader of the New Model Army in the second English civil war, Cromwell helped repel the Royalist invasion of Scotland, and in 1646 Charles surrendered to a Scottish army. In 1648, Charles was forced to appear before a high court controlled by his enemies, where he was convicted of treason and sentenced to death. Early in the next year, he was beheaded.

The monarchy was abolished, and Cromwell assumed control of the new English Commonwealth. In 1658, Cromwell died and was succeeded by his eldest son, Richard, who was forced to flee to France in the next year with the restoration of the monarchy and the crowning of Charles II, the son of Charles I. Oliver Cromwell was posthumously convicted of treason, and his body was disinterred from its tomb in Westminster Abbey and hanged from the gallows at Ty burn.

"a government in which power is divided between state and national levels". federalism is a system of government in which entities such and state and province, share power with the national government.