Highly commended for his war service, Oswald later took an interest in politics, unsuccessfully attempting to enter parliament but using his influence in the army to support the Conservatives.

In approximately 1785 he was sent to school in France, the prestigious military academy at Brienne-le-Château, where he formed a lasting friendship with Louis-Antoine Fauvelet de Bourrienne, future secretary to Napoleon.

[1] At the outbreak of the French Revolutionary Wars, the 35th was ordered to the West Indies, Oswald resigning his appointment as a staff officer (brigade major) to accompany them.

In this role he participated in the capture of Martinique, St Lucia and Guadeloupe and the invasion of San Domingo, before being sent back to Britain in 1795 to act as a recruiting officer.

Oswald was particularly noted for his actions in the storming of a Turkish trench line that forced the Ottoman troops to retreat into Alexandria's city walls.

After the surrender of the city, Oswald advanced to Rosetta and there fought a running battle for fifteen days against superior Turkish forces before being ordered to withdraw.

[1][11] In 1810, still in the Adriatic, Oswald gathered 2,000 British and Greeks soldiers and invaded Santa Maura, capturing the island in eight days despite some heavy fighting.

[1] Following Vittoria, Oswald lead the division to the Siege of San Sebastian, but was replaced by the returning General James Leith two days before the assault on 31 August.

Oswald remained a popular figure in British society and politics until his death, noted for his bravery, good looks, public speaking and literary tastes.