The Battle of Naseby was the key battle of the first

First English Civil War

The First English Civil War began the series of three wars known as the English Civil War . "The English Civil War" was a series of armed conflicts and political machinations that took place between Parliamentarians and Royalists from 1642 until 1651, and includes the Second English Civil War and...

 English Civil War

English Civil War

The English Civil War was a series of armed conflicts and political machinations between Parliamentarians and Royalists...

. On 14 June 1645, the main army of King Charles I

Charles I of England

Charles I was King of England, King of Scotland, and King of Ireland from 27 March 1625 until his execution in 1649. Charles engaged in a struggle for power with the Parliament of England, attempting to obtain royal revenue whilst Parliament sought to curb his Royal prerogative which Charles...

 was destroyed by the Parliamentarian

Roundhead

"Roundhead" was the nickname given to the supporters of the Parliament during the English Civil War. Also known as Parliamentarians, they fought against King Charles I and his supporters, the Cavaliers , who claimed absolute power and the divine right of kings...

 New Model Army

New Model Army

The New Model Army of England was formed in 1645 by the Parliamentarians in the English Civil War, and was disbanded in 1660 after the Restoration...

 commanded by Sir Thomas Fairfax

Thomas Fairfax, 3rd Lord Fairfax of Cameron

Thomas Fairfax, 3rd Lord Fairfax of Cameron was a general and parliamentary commander-in-chief during the English Civil War...

 and Oliver Cromwell

Oliver Cromwell

Oliver Cromwell was an English military and political leader who overthrew the English monarchy and temporarily turned England into a republican Commonwealth, and served as Lord Protector of England, Scotland, and Ireland....

.
At the beginning of 1645, most of King Charles's advisers urged him to attack the New Model Army while it was still forming. However, Prince Rupert of the Rhine

Prince Rupert of the Rhine

Rupert, Count Palatine of the Rhine, Duke of Bavaria, 1st Duke of Cumberland, 1st Earl of Holderness , commonly called Prince Rupert of the Rhine, KG, FRS was a noted soldier, admiral, scientist, sportsman, colonial governor and amateur artist during the 17th century...

, who had recently been appointed General of the Army and therefore the King's chief military adviser, proposed instead to march north to recover the North of England and join forces with the Royalists

Cavalier

Cavalier was the name used by Parliamentarians for a Royalist supporter of King Charles I and son Charles II during the English Civil War, the Interregnum, and the Restoration...

 in Scotland

Scotland

Scotland is a country that is part of the United Kingdom. Occupying the northern third of the island of Great Britain, it shares a border with England to the south and is bounded by the North Sea to the east, the Atlantic Ocean to the north and west, and the North Channel and Irish Sea to the...

 under Montrose

James Graham, 1st Marquess of Montrose

James Graham, 1st Marquess of Montrose was a Scottish nobleman and soldier, who initially joined the Covenanters in the Wars of the Three Kingdoms, but subsequently supported King Charles I as the English Civil War developed...

.