By mid-May Coburg was reinforced to a strength approaching 90,000, which allowed the Allies to drive the French from an entrenched camp in the Battle of Famars on 23 May, and lay siege to Valenciennes.

The British government were surprised by this, the British were inexperienced in heavy siege warfare and lacked equipment, it was even suspected the Austrians had some sinister reasons for choosing York [2] York's Chief of Engineers Colonel James Moncrief believed that the place could be carried by an assault without the need for a long protracted investment, but Ferraris would hear none of it and insisted on a formal siege of trenches following full procedures.

[3] On 26 July, the main hornworks on the Eastern side were stormed by three columns, one of them of British troops (companies of the Guards supported by part of Abercromby's brigade).

Knowing the Duke's wishes on that head, convinced of the folly of such a measure, and strongly supported by Colonel Moncrieff, I gave positive orders to the contrary, which was approved in the fullest manner by His Royal Highness who was at that time at a redoubt a little to the rear".

[5] Following the fall of the hornwork Valenciennes surrendered on 28 July, the garrison being allowed to leave with the honours of war minus their weapons and munitions.