During the
English Civil War, Spring was among
Parliament's most active supporters in East Anglia. Following the outbreak of hostilities in October 1642, he was appointed to all the local commissions in Suffolk organised to prosecute the war against Charles I. Spring travelled the eastern counties of England, helping to recruit soldiers to the Parliamentarian army and maintain Parliament's control of East Anglia. In late 1642, he and
Samuel Moody raised over £7,500 from among Suffolk residents as a contribution to the Roundhead war chest. In January 1643 he was among those who met in Bury St Edmunds to decide the organisation of the new
Eastern Association. Cromwell intervened, telling Spring that he did not care which social class his soldiers came from, as long as they believed in Parliament's cause. In September 1643, Cromwell wrote to Spring, saying: "I had rather have a plain russet-coated captain that knows what he fights for, and loves what he knows, than that which you call a gentleman and is nothing else". In February 1644, he was appointed a joint-treasurer and receiver-general of the Eastern Association by the
Earl of Manchester. In January 1645, Spring was sent by the Eastern Association to lobby the
Committee of Both Kingdoms regarding the introduction of the
New Model Army. ==Member of Parliament==