London's alignment with parliament in the English civil war was never a foregone conclusion. Though historians have long identified the City as a stronghold for parliament, it could scarcely be called 'parliamentarian'. So how and why did the largely conservative City provide much of the financial and military support needed to wage an effective war against Charles I? For the first time, Civil war London reveals the dynamics of London's support for parliament. It investigates the series of episodic, circumstantial, and ultimately unique mobilizations that allowed war to be maintained from the outbreak of the Irish rebellion in late 1641 through to the establishment of the New Model Army in early 1645. Based on research from two-dozen archives, the book charts the successes and failures of London's financial and military mobilizations and countermobilizations, challenging longstanding notions about the wartime capital. Revealed in the process are interactions between London's Corporation, parochial communities, and livery companies, between preachers and parishioners, and between agitators, propagandists, and common people. Within these tangled webs of political engagement lie the untold stories of the movement of money and men, but also of parliament's eventual success in the English civil war.