page_title: Action of 21 May 1918
section_title: Action
hierarchical_section_title: Action of 21 May 1918 / Action
caption_attribution_description: English: Lieutenant Commander Daniel A. J. Sullivan, United States Naval Reserve Force. Portrait photograph, taken circa 1920. Sullivan was awarded the Medal of Honor for "extraordinary heroism" while serving in USS Christabel (SP-162) during an action with a German submarine on 21 May 1918. He was a Naval Reserve Force Ensign at that time. Note the "overseas service" chevrons on his uniform sleeve.
context_page_description: The Action of 21 May 1918 was a naval engagement of World War I fought between an American armed yacht and a German submarine in the Atlantic Ocean off Spain.
context_section_description: Once the allied convoy was within 2 mi (1.7 nmi; 3.2 km) of Île d'Yeu, a well-defined oil slick was sighted between the American warship and the British steamer, off Danse′s port bow. Christabel cruised over to the slick for better observation but saw nothing to further indicate a German submarine's presence. The convoy continued for a little while when at 17:20 the wake from UC-56 was spotted by the officer-of-the-deck and a lookout, about 600 yd (550 m) off the port quarter.
  Christabel was—at this time—about 300 yd (270 m) from the port bow of Danse. Christabel headed for the wake, making all possible speed, which was around 10.5 knots (19.4 km/h; 12.1 mph), whereupon the wake disappeared and a number of oil slicks were seen. The U-boat had apparently submerged. The American commanding officer ordered his ship to follow this oil for as long as possible and at 17:24—believing that his ship was just ahead of the submarine—Christabel′s crew dropped a depth charge, but nothing resulted although the charge exploded.
  The action was over for now and the allied vessels continued northward. At 19:00, the convoy changed course, following the contour of the Spanish coast, making about 9 knots (17 km/h; 10 mph) for almost two hours when Christabel encountered the German U-boat once again. This time at 20:52, Christabel was astern, making about 11 knots (20 km/h; 13 mph) to catch up with the convoy. The German submarine was sighted by lookouts who witnessed a periscope roughly 200 yd (180 m) off the starboard beam.
  Her commander was quickly notified, and Christabel turned toward the U-boat when the periscope disappeared under the water. At 20:55, a depth charge was dropped which detonated 10 seconds afterward. A second charge was dropped a few moments later. No secondary explosion was heard after the explosion of the first charge but after the sound of the second depth charge a third, "very violent", explosion was heard which threw up a large water column close to Christabel's stern.
  An "enormous" amount of debris from the damaged submarine was seen, mixed in with the water column of the third explosion. Christabel was then ordered to turn and cruised in the vicinity of UC-56's position when she was engaged. The crew of the American armed yacht noticed a quantity of thick, black oil and splintered pieces of wood. There were also very large oil bubbles rising to the surface, no doubt belonging to UC-56.
  Sometime during the dropping of the depth charges, a number of other charges—which were prepared and live aboard Christabel—were shaken lose and Ensign Daniel Augustus Joseph Sullivan reacted quickly by jumping on top of them and securing the charges before they could detonate. Sullivan would later be awarded the Medal of Honor for "extraordinary heroism" in this action.
caption: Daniel Sullivan, MOH.
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