A good deal of his early career was spent as aide-de-camp to his brother Jean-de-Dieu Soult who became Marshal in 1804.

[1] When the Army of Sambre and Meuse crossed the Lahn River on 20–21 September 1795, Jean-de-Dieu Soult's brigade led Poncet's division.

Pierre Soult, who served as his brother's aide-de-camp, led a group of soldiers across the river and held a small bridgehead until the rest of the brigade arrived.

Soult saw that the cavalry was missing the ford, so he dashed back to the bank, just as General of Brigade Louis Klein fell off his horse and began to sink.

Soult swam out and saved Klein's life, earning him a letter of thanks from the French government.