In 1572, war loomed large over the Kingdom of England. Queen Elizabeth I set in motion a plan to form militia units in every province of England, including the environs of the City of London. Called the Trayned Bandes, this organization was comprised of the responsible men of the counties and the towns therein, who mustered periodically for training in the art of war.

By 'responsible men,' we mean the prosperous yeoman farmers and husbandmen, as well as artisans and merchants of the towns. These were the 'middling sort' of Elizabethan and Stuart England, and they were the non-commissioned officers, and rank and file. The 'poorer sort', cottagers, who lived in a rented home and worked the land either for wages, or short term tenants on a farm, and apprentices, servants, and labourers were to be excluded, because it was felt that they had no real stake in the economy, and social order. Also, it was felt that giving them weapons and training would only encourage them to mischief. The aristocracy and gentry, the 'better sort', the 'natural' leaders of society, would provide the officers. They would also provide men out of their household (servants and tenants); in this manner the 'poorer sort' were often were included in the ranks.

At that time England had no standing army, so the Trayned Bandes were the only forces which could be called upon in times of strife. The Bands were supposed to drill at least once a month, usually a Sunday afternoon at the end of divine services, in the churchyard or on the commons, but frequently it was much less, since nobody wanted to drill in winter and after 1588 England was not seriously threatened with invasion. The Trayned Bandes often could and did hire professional soldiers who had seen active service on the continent to be the muster master (picture a 17th-century version of a Army drill sergeant) and keep the equipment in good repair.

While the provincial Trayned Bandes were often of indifferent quality due to lack of training, London was different. Its Trayned Bandes were very good; the members took pride in their service, for it was fashionable to serve. Some were better than others but training, quality of equipment, and maintenance thereof was higher than the usual in the provincial Bandes.

The London Trayned Bandes did not participate as units in the out-of-kingdom wars fought by Charles in futile attempts to maintain his personal, absolute rule. The disastrous Bishop's Wars in 1639 and 1640 did, however, directly result in the Long Parliament, which sat from 1640 until the establishment of the Cromwellian Protectorate. Charles was forced first to beg this Parliament for funds to fight his campaigns, then to ask for more cash to bribe the victorious Scots from the north of England, which they had occupied. Parliament, however, demanded numerous political concessions for their money, including the impeachment of Charles' two most important lieutenants: the Earl of Stafford, Thomas Wentworth, and the Archbishop of Canterbury, William Laud.

Then in 1641 Ireland (with Stafford no longer there to repress everyone) revolted, and Parliament and the king fought other for control of the army which was to put down the rebellion. The King considered himself commander-in-chief of all military forces and Parliament was too frightened to allow him sole control; they feared that he might used the army against them, Englishmen, first. In January 1642 Charles attempted to arrest 5 if his most vocal opponents in the House of Commons. The five 'birds' flew before Charles arrived and he was hooted out of Commons. Rioting broke out in the city and Charles fled. With this breakdown of relations between King Charles I and The Long Parliament, both sides began to prepare for war. London declared itself for Parliament, as did all its Trayned Bandes.

Before the outbreak of the English Civil Wars, the City fielded four regiments, named for the four cardinal points of the compass. In 1642, two more regiments were raised, and the regiments renamed to correspond with the hue of their colours (flags). The Blew Regiment of the Cittie of London Trayned Bandes was comprised of approximately 1200 musketeers and 800 pikemen drawn from the citizens of London, generally members of the various trade guilds. Upon the outbreak of the First English Civil War in 1642 London declared for the Parliamentarian cause, as did its Trayned Bandes. The Blew Regiment was involved in most of the significant battles of the First War, which culminated in the Battle of Naseby in 1645 where the armies of Charles I were finally defeated.