As the eldest son, Henry succeeded William as Count of Eu and Lord of Hastings.

In 1101, he supported Duke Robert Curthose against his brother Henry Beauclerc who has just seized the English throne.

He fought for the king at the Battle of Tinchebray in 1106, where Duke Robert was taken prisoner, to remain in captivity for the rest of his life.

Henry joined the cause of William Clito, the son of Duke Robert, in the coalition composed of Baldwin VII of Flanders, Fulk V of Anjou, and Louis VI the Fat.

In the following month, he took part in the defense of the town of Breteuil, which was attacked by the French king and his ally Amaury III of Montfort.