Erlach was born in Bern into the noble Erlach family.[1] His father, also called Karl Ludwig von Erlach, was a colonel and bailiff.[1] Erlach began his career as an officer of the Swiss Guards in French service.[1] In 1774, he was promoted to colonel and given command of the Schomberg Dragoons regiment, and the next year he was made a Knight of the Order of Military Merit.[1] Erlach reached the rank of maréchal de camp in 1790.[1]
He was a member of the Grand Council of Bern since 1775.[1] In 1791, after returning to Switzerland, Erlach commanded the Bernese troops sent to suppress a revolt in Vaud.[1]
When Revolutionary France invaded the Swiss Confederation in February 1798, Erlach was appointed supreme commander of the Swiss Army by the Confederation's War Council.[1] Although he developed a defensive plan, Erlach could not implement his strategy due to the interference of the War Council, and was defeated by General Balthazar Schauenburg at the decisive Battle of Grauholz on 5 March.[1] After the battle, Erlach began a retreat to the Bernese Oberland, where he planned to continue resistance against the French.[1] Later that day, near Wichtrach, Erlach was assassinated by his own soldiers, who mistakenly believed him to be traitor.[1]
