The answer is **no**. Cardigan did not serve in the Napoleonic Wars. He was born in 1797, and the Napoleonic Wars ended in 1815. Cardigan was too young to have participated in the wars, which were primarily fought between 1803 and 1815.
The Quintessential Quizzmaster: Unravel the Enigmatic Life of James Brudenell, 7th Earl of Cardigan!