8.2 17

The heat is doubled as four master smiths compete alongside their apprentices to forge an iconic weapon of warfare-the trench knife. Each team must work together, tagging in and out every half hour, with only one smith allowed to touch the knife at a time. Blood is spilled and tears are shed. Refusing to retreat, two teams square off in one final battle to recreate a blade that's stood the test of time-the Chinese Dao Sword.