Otway's service in quelling the uprising is not clear, but he was certainly present at the Battle of Vinegar Hill on 21 June 1798, when his unit was employed in riding down the panicking rebels at the collapse of the rebellion.

Returning to Europe in 1807, Otway volunteered for service in Portugal and Spain with the 18th Light Dragoons and was attached to Sir Arthur Wellesley's army, although he did not see any action before the temporary peace treaty.

With this force, Otway was repeatedly engaged, including service at the Battle of Busaco in 1810 and a victory at Campo Mayor in 1811 which was wasted by the profligacy of his senior officer Robert Ballard Long.

[1] However, Long was of the opinion, and was subsequently supported in this by the historian William Napier, that it was Beresford's refusal to release the British brigade of heavy dragoons that led to the escape of the French force.

In 1812, Otway had returned to England but continued service, formulating a plan to raise a cavalry regiment of non-French prisoners of war which was ultimately rejected.

[1] Frustrated, Otway returned to Portugal and was employed for the remainder of the Peninsula War training Portuguese and Spanish cavalry regiments.