[2] Egerton would begin his army career in 1793 as an Ensign in the 29th Regiment of Foot.

During his service in the 29th, Egerton, now a Lieutenant, commanded a group of the 29th as marines on HMS Thunderer during the Glorious First of June in 1794.

[3][4] In 1798 Egerton was promoted Major of the 89th Regiment of Foot, where he saw action in the Irish Rebellion of 1798 taking part in the Battle of Vinegar Hill.

After the rebellion, Egerton and the 89th foot were posted in Malta in 1800, and in 1801 transferred to Egypt for the Egyptian Campaign where he took part in the Battle of Alexandria and the Siege of Cairo.

Egerton continued with the 44th foot throughout the Peninsular War, eventually commanding a whole brigade of the 5th Division.