The Ottoman fleet supported the French by ferrying the French troops under Marshal de Thermes from Siennese Maremma to Corsica. The Ottoman fleet of Dragut was at that time party to a Franco-Ottoman alliance. In June 1549, de Thermes was sent to Scotland to help in the war against England now called the Rough Wooing.
He was instructed to continue the fortification of border strongholds, and came with massive reinforcements, munitions and money.
Subsequently, the English abandoned their occupation of Haddington, a town near Edinburgh, and de Thermes and Regent Arran walked in. Mary of Guise was triumphant, writing that, "the English had left nothing behind but the plague." De Thermes led the successful assault on the English fort at Broughty Castle on Wednesday 6 February 1550.
Following a recommendation by Mary of Guise on 30 September 1549, he was made a knight of the Order of Street Michael for his service in Scotland. Back in France, Paul de Thermes lost the Battle of Gravelines in 1558.