During the Civil War the county of Cornwall was entirely loyal to King Charles I and the Royalist cause.

Each side understood that if they were to either invade the other county or defend against invasion, they had to have control of the Tamar's crossings.

[1] The Parliamentarian forces, headed by Robert Devereux, 3rd Earl of Essex, pushed into Cornwall over the bridge.

Lord Essex travelled north to Launceston, leaving half of his troops defending New Bridge.

On the 26th of July Essex crossed the Tamar at Horsebridge, penetrating the Royalist defences and continuing into the heart of Cornwall.