In the "Breakdown" mission in the "Through Mud And Blood" war story, proceed along the road to the French village where you need to collect parts for your broken tank. This is the village with the windmill on the hill overlooking the town. Once you reach the village, look for a two-story house on the left with a mounted machine gun on the balcony and a soldier looking out the window, directly above a corner door. This is a building on the main street, near the edge of the town facing the windmill. Directly beneath the machine gun turret is the Cavalry Sword under a table on the first floor.