East Anglia staunchly supported Parliament against the King, and on 20 December 1642 the Eastern Association was formed to martial forces and money to Parliament’s cause. Membership was originally the counties of Norfolk, Suffolk, Essex, Cambridgeshire and Hertfordshire, and expanded in 1643 to include Huntingdonshire and Lincolnshire. Its headquarters were at Cambridge, and the site of Cambridge Castle was again brought back into military use as an artillery fortress.
Cambridgeshire’s proximity to the King’s headquarters at Oxford and its position adjacent to the Great North Road meant it was vulnerable to Royalist attack. Cambridge Castle itself was the first major defence to be constructed, and other measures were taken to protect the city, with the bridges being pulled down, and defence works built at Four Lamps and Jesus Lane. A bank and ditch may run alongside the current line of Lensfield Road.
Elsewhere in Cambridgeshire, defences were constructed at various locations in response to specific threats. These included a line from Wisbech to Guyhirn fortified in 1643 after the Royalist capture of Lincolnshire. In Wisbech itself, the castle drawbridge was repaired.
Initial Royalist success in 1644 saw the construction of the fortress at Horsey Toll near Peterborough, and the creation of artillery bastions at Huntingdon Castle. In 1645, despite the Parliamentarian victories at Marston Moor (1644) and Naseby (1645), the perceived threat of Royalist invasion of Cambridgeshire resulted in the construction of Earith Bulwark, positioned to control access along the River Ouse and adjacent road. However, the invasion never materialised, and with the end of the war the fortresses and bastions were no longer required so were slighted to prevent them being used in any uprising.
In March 1643 the Eastern Association mustered its “trained bands” at Cambridge. These men were not professional soldiers, but levies from the towns and communities of the region. The initial reaction to the muster was lukewarm, and although the cavalry were regarded as being of an acceptable standard, the infantry in particular were regarded as badly paid, equipped, organised and commanded.
The regiments of the Eastern Association first saw action in May 1643, but a major change took place on 8 August 1643 when Edward Montague, the Earl of Manchester who lived in Kimbolton, became its Major General, and Oliver Cromwell was appointed Lieutenant General of cavalry. Under this new regime, the military effectiveness of the Eastern Association was demonstrated by victory at the Battle of Winceby on 11 October 1643, and cumulated in the decisive victory over the Marquis of Newcastle’s regiments at the Battle of Marston Moor on 2 July 1644.
This victory of the Eastern Association formed the turning point in the war, as it not only destroyed the most successful Royalist force, it also showed what tactics and training were most effective against the generally superior Royalist troops. These lessons resulted in the formation of the New Model Army of Parliament, which finally destroyed Royalist hopes of victory.by