The Long Blue Line: McCormick & Thetis—the Coast Guard’s forgotten sub-killers

The cutter tracked her target doggedly and forced the sub to remain submerged for long intervals until the appearance of continuing oil slicks, debris and clothing gave evidence of the probable destruction of the hostile vessel.
Legion of Merit Medal citation, Lt. Nelson C. McCormick, commanding, Coast Guard Cutter Thetis

During World War II, the Coast Guard cutter Thetis (WPC-115) was one of 11 cutters credited with sinking U-boats. One of the “B”-Class 165-foot cutters and the namesake of its class, Thetis is all but forgotten by most histories of the Coast Guard.

Thetis and its sister cutters were designed for Prohibition enforcement, specifically apprehending rum running ships off the U.S. coast. The cutters had excellent sea-keeping qualities, long-term accommodations for crew and good fuel capacity. Thetis was built by Bath Iron Works in Maine and commissioned on Dec. 1, 1931. The cutter reported for duty at Staten Island, New York, and served as part of the New York Division’s Special Patrol Force, which conducted law enforcement patrols in support of Prohibition. In 1933, after passage of the 21st Amendment repealing Prohibition, Thetis was assigned to Boston for law enforcement and search and rescue patrols.

After war erupted in Europe in 1939, the Coast Guard assigned Thetis to the U.S. Navy’s East Coast Sound School in Key West, Florida. After the 1941 entry of the U.S. into World War II, Thetis joined three of its sister cutters in Key West as part of the Navy’s Gulf Patrol, which performed escort duty for coastal convoys and anti-submarine patrols around Florida and the Caribbean. When built, Thetis was about 337 tons fully loaded with five officers and 39 enlisted men. However, after the wartime addition of 20 mm guns, radar and sonar gear, two depth charge racks and a Y-gun used for depth charging, Thetis gained 30 more officers and men and 15 added tons over the cutter’s pre-war configuration.

The commander of Thetis, Lt. j.g. Nelson C. McCormick, was a native of Dayton, Texas. A late bloomer, McCormick graduated from the Coast Guard Academy near the bottom of the Class of 1935 at the ripe age of 27. He received a temporary commission upon graduation and a permanent one two years later. By the late 1930s, McCormick had served on three different cutters and commanded the 165-foot cutter Dione. Prior to his command of Thetis in Key West, McCormick had also served off the North Carolina coast, also known as “Torpedo Junction,” and accrued experience hunting U-boats.

The U-157 was a Type IXC U-boat commanded by Korvettenkapitän Wolf Henne with a crew of 51 officers and men. In May 1942, Germany’s Kriegsmarine ordered U-157 to deploy on a war patrol from Lorient, in Nazi-occupied France, to destroy shipping in the Caribbean. The U-157 was 250 feet long with two propellers and a test depth of 750 feet. It carried 22 torpedoes with four tubes in the bow and two in the stern, and it was barely a year old when it began this second of its war patrols.

On Tuesday, June 9, 1942, while carrying out its normal training and patrol duties off the southeast coast of Florida, Thetis took part in an unsuccessful search for what was thought to be a U-boat. On Thursday, U-157 torpedoed and sank the 6,400-ton tanker SS Hagan off Cayo Guajaba, Cuba. The next day, a radar-equipped U.S. Army B-18 “Bolo” bomber was sent out to search for the sub. Finding U-157 on the surface, the bomber failed to drop depth charges on its first pass, but turned sharply, sped back to the sub and dropped four depth charges near the crash-diving sub. The depth charges missed and Henne, his crew and U-157 narrowly escaped.

By Saturday, Thetis received word that a periscope had been spotted in the Florida Straits. With McCormick in command, Thetis sped toward the location to join a Navy “hunter killer” group of radar-equipped B-18s, three destroyers, several patrol craft, and Thetis’ sister cutter Triton. In conjunction with the hunter killer group, Thetis began searching for the U-boat at 2:30 p.m. An hour later, the soundman on Thetis heard a clear contact on the bottom.

Having performed this operation many times before, McCormick did not hesitate. He ordered the cutter to battle stations while Thetis steamed 1,000 yards beyond the contact. Next, he turned the cutter back toward the target and ordered full speed ahead to start the first depth charge run. The sonarman regained contact and Thetis bore down on U-157’s position at 14 knots. McCormick attacked the sub with six depth charges, released at five-second intervals, and two more from the ship’s “Y” gun at the same time as a final depth charge. The charges were set at 200 and 300 feet and fell all around the German sub.

After making the run and observing the depth charge explosions, Thetis turned to starboard to observe the results of its attack. A short distance to the right of the cutter’s wake, the crew noticed a “water slug,” which did not resemble the disturbance made by depth charge explosions. Around 4:15, Thetis’ crew observed pieces of freshly broken wood and clothing float to the surface. McCormick maneuvered Thetis into the debris field and crew members retrieved two pairs of leather pants of the type worn by German submariners and a tube of lubricant made in Germany. Navy patrol craft soon arrived to assist in the kill while Thetis steamed back to base at Key West to take on more depth charges. Thetis returned from Key West and performed one more depth charging, but this run proved unnecessary for Thetis had sunk U-157 with its first depth charge run. U-157 had been destroyed along with Henne and the U-boat’s 51 crew members.

Thetis had become the third American warship to sink a U-boat and the second Coast Guard cutter to do so. For his command of Thetis in the attack and sinking of U-157, McCormick received the Legion of Merit Medal. Later, McCormick received promotion to lieutenant commander and command of the new Coast Guard-manned patrol frigate, USS Reading. Besides McCormick’s Legion of Merit Medal, Thetis and its commander received very little attention or recognition for the elimination of U-157 and the threat it posed to shipping in Florida’s waters. McCormick retired from the service in 1946 and the Coast Guard decommissioned Thetis in 1947 selling it out of the service in 1948. The 165-foot Thetis was one of many combat cutters that served under the heroic Coast Guardsmen of the long blue line during World War II.