Short answers, pulled from the story.
The government of the Kingdom of France appointed Jean-Baptiste Donatien de Vimeur, Comte de Rochambeau as its commander on the 14th of December 1791. This appointment marked the official creation of the Army of the North.
Napoleon Bonaparte commanded the force known as the Army of the North during the Waterloo Campaign in 1815. The army numbered 130,000 strong at its height and included many veterans from previous campaigns.
On the 25th of October 1797, the Army of the North officially ceased to exist. Its troops became an army of occupation in the newly created Batavian Republic.
The Army of the North suffered a crushing defeat at the Battle of St. Quentin where it was scattered. Severe supply difficulties, low morale, terrible winter weather, and General Faidherbe's poor health contributed to this failure.
The Army of the North in Spain formed in January 1811 and included soldiers from the Imperial Guard. This unit fought guerillas and held cities and fortresses in northern Spain until June 1813.