In the spring of 1809, the Irish Legion was given a new name and organisation. By a decree dated 13 April, the Emperor established the 3rd Foreign Regiment as a French light infantry regiment. About the same time it was decided to raise a 3rd Battalion and John Tennant, as the senior captain, with four officers from the 1st Battalion were ordered to Landau to from the nucleus of the new battalion. As such he missed the English landing on 30 July 1809. On 9 November he was promoted to the rank of "chef de bataillon" and named commandant of the new 4th Battalion.