On the 10th August 1512, the Battle of Saint-Mathieu, a battle in the War of the League of Cambrai, took place between the English and Franco-Breton fleets off the coast of Brest. England at this time was allied with Spain and the Holy Roman Empire against France.
As the Mary Rose Museum points out, it was the Mary Rose's first battle and she was chosen as the English fleet's flagship by Sir Edward Howard, Admiral of the English fleet. Howard, who was moored with the English fleet at Portsmouth, had heard that the French fleet had gathered at Brest and so set off to meet them. The two fleets met in Berthaume Bay, near Brest, om 10th August and the battle began.
France had twenty-one ships, including the flagship the Grand Louise and the Marie La Cordelière, while England had twenty-five ships, including Henry VIII's largest ship, the Regent, and the new and smaller Mary Rose. The Mary Rose museum website states: