At the age of twenty he took part in the assault against the stronghold of Angoulême held by the League and captured the lieutenant of the city. In 1587 he distinguished himself at the battle of Coutras. He fought against the Leaguers of the Duke of Mayenne at the battle of Arques (1589) and the battle of Ivry (1590), scoring victories that opened access to Paris for the future monarch of France. Henry, who abjured his Protestant faith in 1593 and was crowned in Chartres in 1594, entrusted Fouquet with public diplomatic missions as well as confidential matters.