German U-boats torpedoing the Soo Locks? During WWII, the threat seemed real enough.

Could Adolph Hitler’s German army penetrate an isolated peninsula in the Great Lakes? During World War II, America’s generals feared they might—especially given that 90 percent of the country’s iron ore sailed through the Soo Locks, located in the Northern Michigan city of Sault Ste. Marie.

What to do? Send 7,000 American troops to defend the locks. Sault Ste. Marie author/historian Bernie Arbic (City on the Rapids) tells us more about this little-known aspect of World War II history.

Special thanks to the Chippewa County Historical Society for help in the production of this video.

Read the full story as seen in Traverse Magazine.