Alexander Leslie, 1st Earl of Leven, Lord Balgonie was born in 1580 and died on the 4th April, 1661, at Balgonie, Fife, Scot. Alexander was the son of captain George Leslie, and a member of the family of Leslie of Balquhain. 

He married in 1637 to Agnes Renton (d 29.06.1651, dau of David Renton of Billie), and in due course his eldest son, Gustavus Leslie became a colonel in the Swedish army. Alexander Leslie joined the Swedish army in 1605 and distinguished himself several times during the Thirty Years War serving in the Swedish army for about 33 years. By 1626 Alexander Leslie had risen to the rank of lieutenant-general, and had been knighted by the king of Sweden, Gustavus II.   Sir Alexander Leslie was badly wounded in the winter of I632, but was promoted again in 1636 to the rank of field marshal, but by 1638 events in England compelled him to return to Scotland to lead the army of the Covenanters in the Bishops Wars. Scottish regiments were generally called into service by the lairds and clan chieftains obliging their tenants with feudal duty or coercion to send their kin to follow the Covenanters’ banner into battle.The flag bore the motto 'For Christ's Crown and Covenant' and appeared in 1639 before the Covenanter army commanded by General Alexander Leslie, 1st Earl of Leven, an ardent Covenanter.

His reputation, guile and discretion, brought even the rebellious Scottish lords to his subordination. Having amassed a considerable fortune abroad he was able to bring from Sweden his arrears of pay in the form of cannon and muskets which he were no doubt put to use in taking the castle of Edinburgh by surprise, without the loss of a single man, for the king and against Parliament. 

In 1641 King Charles bestowed upon him at Holyrood, the title of earl of Leven and Lord Balgonie, and made him captain of Edinburgh Castle and a privy councillor.

Leven eventually accepted command of the forces raised for the invasion of England, and was in consequence accused of having broken his personal oath to Charles. He rose in stead to become a commander of the Scottish army from 1644 to 1646 and fought on the side of Parliament.

In 1644 Leven commanded an army which he marched to England to take part in the battle of Marston Moor, a crushing defeat for the king. When Charles surrendered to the Scottish army again in 1646, he was placed under the charge of General Alexander Leslie and was returned to the English in 1647. 

Although over seventy years of age, and still active Leven passed active command of the army to his nephew David Leslie in whom he had complete confidence, before the Scottish Covenanters (then royalist) were defeated (1650) at the battle of Dunbar.

"In the new war, and in the disastrous campaign of Dunbar, Leven took but a nominal part, though attempts were afterwards made to hold him responsible".

In August, 1651 Leven had the misfortune to be captured by a group of English dragoons, and was sent to London. He was confined to the Tower of London for some time, until he was released on providing a bond of £20,000, whereupon he retired to Northumberland. Again sometime later in London he was arrested a second time, but through negotiations with the queen of Sweden he again obtained his liberty. 

External link:
Leslie Family history.