While his father was in Ireland he was educated in Dublin and then later at St.Paul's in London, but learning was not to his taste. He was almost illiterate and his spelling would remain atrocious. After 
his sister Arabella, aged only sixteen, had been appointed as maid-of-honour to the Duchess of York, John Churchill became page to the Duke of York. Another page-boy was Sydney Godolphin and a 
friendship started which would last for many years and which proved to be of political importance. 
What was also of importance was the affair of his sister Arabella with the Duke of York. In 1667 the Duke of York asked him what profession he would choose---and, when he replied he wanted to join 
the army, he was given a commission in the King's Own Company of Foot Guards. He went to Tangier with the army and spent three years there fighting the Moors. 
He returned as an ensign and, having matured as well as being handsome, he was favoured by the ladies. However, it was his cousin Barbara Villiers, Duchess of Cleveland and the King's mistress, who 
got hold of him; and when in July 1672 she gave birth to her last child, it was almost certain that he was the father. As "she was as liberal of her purse as of her person" it was believed she gave him 
œ5,000 and he bought himself an annuity of œ500. He was presumed to fritter away this money and investing itso sensibly gave him the reputation of being avaricious and he was resented for this. 
By the time he was twenty-four he had become a colonel. In 1673 he served with distinction under King Louis XIV of France and was publicly thanked by that monarch. Under Vicomte de Turenne, the 
greatest commander of the day, Colonel Churchill took part in the battle of Enzheim and was mentioned in Turenne's dispatches. In 1675 he returned to England, having learned a great deal from the 
unorthodox Turenne. 
His affair with the Duchess of Cleveland had come to an end and he fell in love with the fifteen-year-old Sarah Jennings. It may be that he fell in love at first sight but he had to wait another three years before he could persuade her to marry him in secret. Their families did not approve, he had no properties or prospects and her father had wanted a titled son-in-law. However, it was a love match and so it would remain all their lives. 
When in 1685 the Duke of Monmouth landed in England hoping to replace the Catholic James II, Lord Churchill of Sandridge, as he was then as well as Brigadier-General, was marching towards Monmouth's army. However, the appointment of commander-in-chief had gone to the less experienced Earl of Feversham, a nephew of Turenne. Churchill complained that he would have to do all the work while the honour would go to someone else. 
They reached Bristol before Monmouth. When the Earl of Argyll's simultaneous uprising had failed which resulted in Argyll being put to death, Monmouth was at first despondent. However, at Sedgemoor he hoped to surprise the royal troops at night. Apparently the Earl of Feversham was asleep, but John Churchill was awake and alerted the troops. After several hours of fighting Monmouth was defeated, captured and later executed. 
Monmouth's co-conspiritors were taken to Judge Jeffreys at the Bloody Assize whose dealing with them was vicious and sadistic. About 400 were hanged and 1,200 were sold as slaves for the Barbados 
plantations. Feversham got the Garter and Churchill was allowed to command the 3rd Troop of Life Guards. However, the unoffical praise went to Churchill. 
This victory encouraged James II in his Catholic policies. Early in 1688 James II's son-in-law, Prince William III of Orange, was invited to come and save England from Popery. However, being cautious and reluctant, he waited until after James II had imprisoned seven opposing Protestant bishops and, as well, Mary of Modena, James II's wife, had given birth to a son. This son would be ahead for the throne of William III's protestant wife Mary and her equally protestant sister Anne. On 5 November 1688 William III landed at Torbay with his army. 
With curious indecision and suffering from insomnia and nosebleeds, James II failed to act. His army should have been sufficient to repulse the invader but soon army officers started to defect. Amongst 
the first of these were John Churchill and the Duke of Grafton, to be followed by the Duke of Ormonde and the Prince of Denmark, the other son-in-law of James II. The shattered James II returned to London only to find his daughter Anne had deserted him as well. James II with his wife and baby son then went into exile in France. 
William III and his wife Mary II became joint sovereigns of England. William III tried to curb the expansionist policies of the French King Louis XIV and, as King of England, was in a better position to do so. John Churchill was ordered to reorganize the army and at the coronation in April 1689 he became Earl of Marlborough. As Earl of Marlborough he went to Flanders and served under the Prince von Waldeck. 
Having trained his army as well as attending to their needs, his troops were superior at the battle of Walcourt in 1689. When in that year James II went to Ireland trying to regain his throne, Marlborough 
also went to Ireland and, after a siege of a week, took Cork on 29 September 1690. He went on and took Kinsale which prevented a possible French invasion. 
As William III and Mary II neither liked nor trusted Marlborough, lucrative posts went to Marlborough's brother Charles Churchill but not to Marlborough. Having been such a trusted servant of James II, 
William III doubted his loyalty and, in 1692, Marlborough did start a secret correspondence with the exiled monarch. However, William III also had objections to the close friendship of Princess Anne with 
Marlborough's wife, Sarah, as Sarah manipulated Anne which resulted in a quarrel between the two royal sisters. Mary II ordered Anne to dismiss Sarah but Anne refused. Mary II persisted but Anne still 
refused to give in. In January 1692, William III dismissed Marlborough from all his offices. As no reason was given, rumour had it that Marlborough had taken bribes but Sarah avowed that Marlborough had never taken bribes and that she herself was the cause of his dismissal. In May 1692 Marlborough was implicated in a Jacobite plot and sent to the Tower; and while in prison his younger son Charles 
died. Lords Halifax and Shrewsbury stood bail and after six weeks he was allowed to leave the Tower, but would remain out of work for six years. 
Sarah still had remained in Princess Anne's employ which even further deteriorated the relationship between the two royal sisters. At this time Anne had given birth to a child and Mary II came to visit 
her, but ignoring the baby and only talking about Sarah. When Mary II left the sisters never saw each other again. In 1694 Mary II died suddenly of smallpox and after a while the relationship between 
William III and Anne improved. Even though Marlborough was still in secret correspondence with James II, by 1698 he had his army rank restored as well as being admitted to the Privy Council. 
In 1700 the Spanish King Carlos II died leaving his inheritance to Philippe of Anjou, a grandson of Louis XIV. Louis XIV accepted on his grandson's behalf, then attacked Dutch fortresses which infuriated the 
Dutch. When James II died, Louis XIV acknowledged his son as King of England which infuriated the English. This allowed William III to create the force which would restrict the French; however he would not see the fruits of his actions as he died in March 1702. 
Two months later the Grand Alliance of England, Holland and the Holy Roman Empire declared war on France. Queen Anne made Marlborough Captain-General and gave him the Order of the Garter, as well as creating him Duke of Marlborough. In July 1702 he was also made Deputy Captain-General of the Dutch Armies. 
In the winter of 1702 Marlborough had secured the navigation of the rivers Rhine and Meuse. However, in February 1703 his son and heir John died only seventeen years old. Depressed by his loss he started 
the 1703 campaign against France, capturing Bonn, but Dutch caution prevented him from capturing Lierre and Antwerp. At first the campaign looked to go well but then the Bavarian Elector defected to the French, opening the way for the French to attack Vienna and destroying the Habsburgs. Knowing his cautious Dutch allies would disapprove, he left a small force in Flanders, and pretending to go to the Moselle area, took off with 21,000 soldiers. Once they reached that area they continued and were joined by Prussian and Hanoverian troops. It still took a while before the French realised that his aim was the Danube and to protect Vienna. For the first time Marlborough met that other military genius, Prince Eugene of Savoy. They immediately liked each other and worked together in total harmony. On 13 August 1703 a battle took place at Blenheim; and that night the decisively defeated French started burning their colours, fearing they might fall into enemy hands. 
When he reached London in December 1703, he was received with great honours and given a pension of œ5,000 for life. Also, at Woodstock the nation would build him a palace to be called Blenheim after his great victory as the power of France now seemed broken. Even though several more years of campaigning followed, the tide did seem to have turned. At home, however Queen Anne had become unhappy with Sarah's continually forcing Whig ideas on her and Sarah fell out of favour, to be replaced in Queen Anne's trust by her own cousin, Abigail Marsham. The year 1708 brought another victory for Marlborough at Oudenaerde; but the same year, when Queen Anne's husband died, Sarah behaved with 
indelicacy and from then onwards stayed away from court. As the peace terms offered to France were outrageous, France refused to sign and another battle followed. On 11 September 1709 Marlborough fought his bloodiest battle. By now Sarah was completely out of favour and Godolphin powerless, both of which weakened Marlborough's position at Court. In August 1710 Godolphin was dismissed, leaving Marlborough without any political support. 
In 1711 Marlborough was accused of malpractice involving œ350,000; although he supplied adequate answers, but still the Cabinet Council still saw fit to dismiss him from all his employments on 31 December 1711. Louis XIV was indeed pleased and even though Marlborough was able to vindicate himself, he was still replaced by the Duke of Ormonde---a sad end to a thirty year association with Queen Anne. Godolphin died in September 1712 and the Duke and Duchess of Marlborough decided to retire to the continent. They were feted everywhere; but after a while the Duchess became homesick and, with the news of the death of their daughter Elizabeth, they decided to go back to England. On 1 August 1714 Queen Anne died and they landed at Dover the next day. King George I reinstated the Duke in all his offices and in 1715 Marlborough was busy with actions against a Jacobite uprising. 
In his later years he was again accused of being too careful with his money. One story has it that he was playing cards with General Pulteney and asked Pulteney if he could borrow sixpence to pay for his 
chair-hire. Pulteney obliged, and the Duke left. Lord Bath, who was there, said "I would venture any sum now that the Duke goes home on foot. Do pray follow him out." Pulteney went to see, and there, sure enough, was the old man trudging to his lodgings. 
In 1716 the death of his favourite daughter Anne triggered off a paralytic stroke which deprived him of speech, but which after a while was partly regained. In 1720 Blenheim at last was fit to live in. 
However, his last few years were marred by the constant quarrels Sarah had with Cadogan, the Duke's aide; with Sunderland, their son-in-law; with Vanbrugh, Blenheim's architect; and as well as with their two remaining daughters, Henrietta and Mary. Even at his deathbed, his wife was still not on speaking terms with their daughters. He died on 16 June 1722.
 

Source: Leo van de Pas