His regiment was posted to North America during the 1754–1763 French and Indian War; he and his youngest son James served in the ill-fated Braddock Expedition and were killed at the Battle of Monongahela, on 9 July 1755.

Pressed by his commander, Prince William, Duke of Cumberland, to break his oath, he refused to do so and was punished by dismissal from the army.

He was re-instated after appealing his case to George II and in 1751 named as colonel of the regiment, which in 1754 was transferred to the British colonies in North America.

[4] The following year, the 44th was assigned to the Braddock Expedition to capture Fort Duquesne (located in present-day Pittsburgh, Pennsylvania, USA) from the French.

The column ran into a combined force of French, Canadian and native Indian troops in the woods and were severely routed.