In the year after the death of the nominal king Robert III of Scotland (1406), in August 1407, Domhnall sent emissaries to England to the heir of the throne, the captive James Stewart.
King Henry IV of England sent his own emissaries the following year to negotiate an alliance against Robert Stewart, Duke of Albany, the Guardian of Scotland who was controlling Euphemia and the earldom.
With control over the principal seat of the earldom of Ross and support of the exiled heir to the Scottish throne, in 1411 Domhnall felt strong enough to march against Albany's main northern ally, Alexander Stewart, Earl of Mar.
At the Battle of Harlaw Domhnall gained the victory (though the Lowlanders claimed otherwise), and withdrew back to his Isles and the Western Highlands.
This action was challenged by Domhnall of Islay, Lord of the Isles, who continued to claim the earldom on behalf of his wife, Mariota.