When the war began, both sides expected it to be decided by a single, decisive battle, but the events of 1642 showed the need to plan for a lengthy conflict.
For the Royalists, this meant fortifying their new capital in Oxford, and connecting areas of support in England and Wales, while Parliament focused on consolidating control of those they already held.
Although peace talks were held in February, neither party did so with any conviction, and they ended without resolution.

The Earl of Essex, commander of the main Parliamentarian army, was ordered to take Oxford, and on 27 April, captured Reading.
Here he remained until mid May, claiming he was unable to advance further without additional supplies, and money.
In response, a convoy was despatched in June, which included £21,000 to pay the soldiers.

The Royalists were even shorter of arms; at the start of the war, Parliament seized the two largest arsenals in England, the Tower of London, and Hull.
They also controlled the Royal Navy, and most of the major ports, making it difficult to import them.
In February, Queen Henrietta Maria landed in Bridlington, Yorkshire, with an arms consignment from the Dutch Republic.

By mid-June, this vital convoy was at Newark-on-Trent, escorted by 5,000 cavalry from the Northern Army; in an attempt to prevent it reaching Oxford, on 17 June, Essex sent 2,500 men to attack an outpost at Islip.
They arrived to find the Royalists waiting, and retreated; as they did so, Scots mercenary Sir John Urry defected, taking with him information on the London convoy, and Essex's troop positions.

Seeing an opportunity, Prince Rupert left Oxford at 16:00 the same day, with 1,200 cavalry, 350 dragoons, and 500 infantry.
Essex had concentrated his troops in the north, exposing his southern positions; concerned by this, John Hampden checked his pickets with care before going to bed.

Many of the troops at Chinnor and Postcombe had just returned from the abortive attempt on Islip, and were exhausted; they failed to post guards, and were taken by surprise when the Royalists attacked at 05:00.
Having inflicted 50 casualties, as well as capturing prisoners and stores, Prince Rupert decided to withdraw before his line of retreat was cut; by 06:30, his forces were on the road back to Oxford.

While three troops under Hampden and Major John Gunter maintained contact with the Royalists, the local commander at Thame, Sir Philip Stapleton, hastily pulled together a force to attack them.
Several senior officers, supposedly in Thame to collect their regiments' wages, helped him form a number of ad hoc units; having collected around 700 men, Stapleton set out in pursuit.
When the war began, both sides expected it to be decided by a single, decisive battle, but the events of 1642 showed the need to plan for a lengthy conflict. For the Royalists, this meant fortifying their new capital in Oxford, and connecting areas of support in England and Wales, while Parliament focused on consolidating control of those they already held. Although peace talks were held in February, neither party did so with any conviction, and they ended without resolution.
The Earl of Essex, commander of the main Parliamentarian army, was ordered to take Oxford, and on 27 April, captured Reading. Here he remained until mid May, claiming he was unable to advance further without additional supplies, and money. In response, a convoy was despatched in June, which included £21,000 to pay the soldiers.
The Royalists were even shorter of arms; at the start of the war, Parliament seized the two largest arsenals in England, the Tower of London, and Hull. They also controlled the Royal Navy, and most of the major ports, making it difficult to import them. In February, Queen Henrietta Maria landed in Bridlington, Yorkshire, with an arms consignment from the Dutch Republic.
By mid-June, this vital convoy was at Newark-on-Trent, escorted by 5,000 cavalry from the Northern Army; in an attempt to prevent it reaching Oxford, on 17 June, Essex sent 2,500 men to attack an outpost at Islip. They arrived to find the Royalists waiting, and retreated; as they did so, Scots mercenary Sir John Urry defected, taking with him information on the London convoy, and Essex's troop positions.
Seeing an opportunity, Prince Rupert left Oxford at 16:00 the same day, with 1,200 cavalry, 350 dragoons, and 500 infantry. Essex had concentrated his troops in the north, exposing his southern positions; concerned by this, John Hampden checked his pickets with care before going to bed.
Many of the troops at Chinnor and Postcombe had just returned from the abortive attempt on Islip, and were exhausted; they failed to post guards, and were taken by surprise when the Royalists attacked at 05:00. Having inflicted 50 casualties, as well as capturing prisoners and stores, Prince Rupert decided to withdraw before his line of retreat was cut; by 06:30, his forces were on the road back to Oxford.
While three troops under Hampden and Major John Gunter maintained contact with the Royalists, the local commander at Thame, Sir Philip Stapleton, hastily pulled together a force to attack them. Several senior officers, supposedly in Thame to collect their regiments' wages, helped him form a number of ad hoc units; having collected around 700 men, Stapleton set out in pursuit.
Battle of Chalgrove Field