In the winter of 1775, the survival of the Continental Army was handed to a 25-year-old Boston bookseller. This episode follows Henry Knox’s 300-mile expedition to haul 59 pieces of artillery, about 60 tons of iron and brass, from Fort Ticonderoga to George Washington’s camp outside Boston, after Benedict Arnold’s earlier effort collapsed into bureaucratic disputes.

We cover Knox’s fireside night with British prisoner John Andre, the sinking and refloating of the gondola on Lake George, the myth of the oxen, the trick of thickening river ice layer by layer, and a mutiny in the Berkshires that Knox defused with showmanship. Then we see how the guns on Dorchester Heights forced the British to evacuate Boston, and how Knox came in at roughly half his 1,000 pound budget.

• Why Washington trusted a self-taught bookseller with a critical military mission
• How the crew bailed out a sunken barge in freezing water and saved the cargo
• Why Knox rented horses in New York before oxen joined the march in Massachusetts
• The engineering behind building up Hudson River ice to carry 5,000-pound cannons
• How fortifications built overnight on Dorchester Heights ended the Siege of Boston