The Trained Bands were local militia regiments organised on a county basis. The system was inaugurated during the reign of Queen Elizabeth I for the defence of the realm. It was controlled by the lords-lieutenant of counties who were expected to appoint professional soldiers to drill the militia and teach them to use the pike and musket.
Membership of the Trained Bands was compulsory for freeholders, householders and their sons, i.e. men who had a stake in the country and were therefore expected to defend it from foreign invasion or local rebellion. In practice, servants and hired substitutes were often sent to attend the training sessions, which were held once a month during the summer.
In addition to the Trained Bands, another form of local militia was the posse comitatus which could be summoned in times of national emergency by the county sheriff. The posse comitatus consisted of the entire capable male population of the county between the ages of 16 and 60.
The Civil Wars
In the absence of a regular army, the Trained Bands were the only permanent military units in England when the Bishops' Wars broke out in 1639-40 and the First Civil War followed in 1642. The popular view was that the Trained Bands were inefficient, poorly equipped and badly disciplined. With a few exceptions, this was generally true of the provincial companies. The London Trained Bands were of better quality thanks to enthusiastic societies of citizens who met regularly during the 1630s to practise their drill, hiring expert soldiers to instruct them. In 1642, the Common Council increased the four regiments of the London Bands into 40 companies of 200 men each, organised into six regiments and distinguished by their colours: Red, White, Yellow, Green, Blue and Orange.
After the battle of Edgehill in October 1642, the London Trained Bands were mobilised to reinforce the Earl of Essex's army in defying the King at Turnham Green. The following year, three more regiments were raised from the boroughs of Westminster, Southwark and Tower Hamlets and an additional six "Auxiliary" regiments were also raised to bring the strength of the London Trained Bands up to around 20,000 men. The Auxiliary regiments were effectively regulars but could not be employed outside London without the permission of the London Militia Committee. Under their popular commander Philip Skippon, the London Trained Bands was one of the most professional fighting forces during the early stages of the war. They held London throughout the First Civil War and contributed infantry brigades to Parliament's field armies, notably in the Earl of Essex's campaign to relieve the siege of Gloucester and the subsequent battle of Newbury in 1643.
Initially, both sides were obliged to rely upon Trained Bands. Many early actions of the First Civil War revolved around attempts to seize the county magazines where their weapons were stored. King Charles simply disarmed the Trained Bands of Nottinghamshire, Leicestershire and Derbyshire and used their weapons to arm volunteer regiments. A major problem was their unwillingness to fight away from their home territories. The Cornish Trained Bands who fought for the Royalist Sir Ralph Hopton in 1643 were reluctant to cross the border into Devon. Even Parliament's London regiments deserted their commander and marched for home during Waller's attack on Basing House in November 1643. Both sides soon came to prefer volunteer soldiers — and used impressment when the initial enthusiasm for the war began to decline.
Local militias continued to train throughout the civil wars. They were mobilised during the Engager invasion of 1648 and again when Charles II led the Scots-Royalist army into England in 1651. At the battle of Worcester, the Essex Trained Bands distinguished themselves by storming and capturing the stronghold of Fort Royal, then turning the guns on the Royalists in the city of Worcester itself.
John Barratt, Cavaliers, the royalist army at war 1642-46, 2000
Philip Haythornthwaite, The English Civil War 1642-51, an illustrated military history, 1983
Stuart Reid, All the King's Armies, a military history of the English Civil War, 1998