The town was garrisoned for the King in January 1643 and began cooperating with the garrison at Newark in raiding the surrounding countryside and harassing Parliamentarians there. With the Great North Road blocked to Parliamentarian traffic, Gainsborough became significant as part of a route around Newark by way of Lincoln and the line of the modern A15 road. It was in Royalist interests to obstruct this, which gave rise to battles at Gainsborough and Winceby. Parliament captured Gainsborough in the battle on 20 July, but it was immediately besieged by a large Royalist army and forced to surrender after three days.