Of peasant antecedents, Kalb was schooled at Kriegenbronn and left home at age 16. He received his first military training in 1743 as a lieutenant in a German regiment of the French infantry, calling himself Jean de Kalb. After a number of years of outstanding service (notably in the War of the Austrian Succession (Austrian Succession, War of the) and the Seven Years' War), he was asked, in 1768, by the duc de Choiseul (Choiseul, Étienne-François de Choiseul, duc de), head of the French Foreign Ministry, to undertake a secret visit to the 13 British colonies in North America to ascertain their attitude toward Great Britain. His four-month investigation resulted in a number of detailed and astute reports. Eager to return to the New World after going back to Europe, Kalb in 1776 secured a promise of a commission in the Continental Army from Silas Deane (Deane, Silas), American commissioner to France. He reached Philadelphia in July 1777 and was eventually appointed a major general by the Continental Congress. He became a strong admirer of General George Washington (Washington, George) and served with him through the trying winter at Valley Forge, Pennsylvania. As second in command to the marquis de Lafayette (Lafayette, Marie-Joseph-Paul-Yves-Roch-Gilbert du Motier, marquis de), he participated in an abortive expedition against Canada (1778).

In April 1780 Kalb was ordered from Morristown, New Jersey, to the relief of Charleston, South Carolina, but the city fell to the British while he was marching south. At Deep River, North Carolina, he was joined in July by General Horatio Gates (Gates, Horatio), commander of the southern department. Kalb urged an immediate attack, but Gates waited until the British forces knew of his presence and then on August 14 marched against them at Camden. The British drove Gates from the field, but Kalb remained in the battle and died five days later from wounds received there.