The Bishops' Wars, a series of armed encounters and defiances between England and Scotland in 1639 and 1640, were part of the Wars of the Three Kingdoms. They led to the King making demands on the English parliament which ignited the English Civil War.
See also the Wars of the Three Kingdoms.
Continuing attempts by King Charles I of England and Scotland to bring the Presbyterian Church of Scotland under his control through imposing bishops and Anglican worship on the Scots came to a head when his imposition of a Book of Common Prayer in 1637 sparked rioting, legendarily started by Jenny Geddes. Opposition to Charles became more formal, with people of all classes showing their open resistance by signing the National Covenant. His attempts to control the situation by diktat from London were futile, and by July 1638 he advised his English Privy Council that he would have to use force. To gain time he agreed to a General Assembly of the Church of Scotland which met at Glasgow in November 1638, but the Assembly firmly decided that bishops were to be deposed or excommunicated and the prayer book abolished. Support for the Covenant grew under the leadership of Montrose and Archibald Campbell, 8th Earl of Argyll, while soldiers serving abroad returned to Scotland, including General Alexander Leslie.
First Bishops' War (1639)
Despite problems in raising funds, Charles gathered a poorly trained English force of around 20,000 men in the early summer of 1639 and marched towards the border. At Berwick-upon-Tweed he was confronted by a better organised force led by Leslie. As neither side wanted to fight, a settlement called "the Pacification of Berwick" was reached in June under which the King agreed that all disputed questions should be referred to another General Assembly or to the Scottish Parliament.
The new General Assembly then re-enacted all the measures passed by the Glasgow Assembly, and the Scottish Parliament went further, abolishing Episcopacy and freeing itself from Royal control.
Charles, believing that the Scots were intriguing with France, fancied that England, in hatred of its ancient foe, would now be ready to rally to his standard. After having ruled alone in England for eleven years, in April 1640 he once more called an English parliament. The so-called Short Parliament demanded redress of grievances, the abandonment of the royal claim to levy ship money, and a complete change in the ecclesiastical system. Charles thought that it would not be worthwhile agreeing such terms even to conquer Scotland, and dissolved parliament. A fresh war with Scotland followed.
Second Bishops' War (1640)
Thomas Wentworth, now earl of Strafford, became the leading adviser of the King. He threw himself into Charles’s plans with great energy and left no stone unturned to furnish the new military expedition with supplies and money. But no skilfulness of a commander can avail when soldiers are determined not to fight.
The Scots under Leslie and Montrose crossed the River Tweed, and Charles’s army was well pleased to fly before them. In a short time the invaders overran the whole of Northumberland and County Durham. (See Battle of Newburn.) Charles had to leave the two counties in Scots hands as a pledge for the payment of Scots expenses when he agreed to peace and signed the Treaty of Ripon in October 1640. The impoverished King had to summon another parliament to grant him the supplies which he needed to make that payment, and a resurgent Long Parliament attacked his Government, impeaching (and eventually executing) his chief supporters, Strafford and Laud.
In the hopes of winning Scottish support, Charles went to Scotland in the autumn of 1641 where he gave titles to Leslie and Argyll, and accepted all the decisions of the General Assembly of 1638 and of the Scottish Parliament of 1641, including confirming the right of the Parliament to challenge the actions of his ministers. He had now withdrawn all the causes of the original dispute, but within a year his disputes with the English Parliament would lead to civil war.
(Original text based on http://1911encyclopedia.org)
The Bishops' Wars: Charles I's Campaigns Against Scotland, 1638-1640 (Cambridge Studies in Early Modern British History) by Mark Charles Fissel ISBN 0521345200
Scotland, A Concise History, Fitzroy Maclean, Thames and Hudson 1991, ISBN 0-500-27706-0