Schlacht bei Neerwinden
Selwyn served in the Army of the United Provinces of the Netherlands, in the time of King Charles II. He served at the head of his regiment at the Battle of Landen on 29 July 1693, distinguishing himself under the eye of the King William III. He then took part at the siege of Namur in the summer of 1695 and was promoted to the rank of Brigadier General during the siege.