He was advanced to post rank on 26 August 1841, and on returning to England went out to China as a volunteer, and at the capture of Chinkiang (Zhenjiang) served as an aide-de-camp to General Sir Hugh Gough.
The government at the time seemed to be in the hands of the army, and Loch forthwith proceeded up the river in the boats of the Alarm and sloop HMS Vixen, his total force being 260 men.
The enemy had occupied a strong position at Serapaqui, defended not only by the nature of the ground and the material obstructions, but by a five-knot current which kept the boats under fire for an hour and a half before the men could land.
It was the time of the Second Burmese War; and shortly after arriving at Rangoon the admiral died; the commodore was off the coast, and the command in the river devolved on Loch.
Loch in person led a joint naval and military expedition against him; landed, and threaded the way by a narrow path through thick jungle.
They found the stockade on the farther bank of a steep nullah, in attempting to cross which they suffered severely and were driven back on 4 February.