SMS U-36 was built at Friedrick Krupp Germaniawerft in Kiel and commissioned on Nov. 14, 1914, she had only one commander in her career, Kapitänleutnant Ernst Gräff. Under his command U-36 sank 14 vessels, the largest being the Norwegian freighter Fimreite at 3,819 tons. He had also taken three prize ships, but the rest were mainly small vessels of less than 1,000 tons, only three others were over that weight. The majority of his successes were made between July 19 and 24 of 1915, in that short period of time Gräff sank thirteen of the fourteen ships.

On the last day, July 24, 1915, Gräff and U-36 were very busy sinking small trawlers north of Cape Wrath, Scotland, three vessels were sunk (Anglia; 107 tons, Cassio; 172 tons, Roslin; 128 tons and Strathmore; 163 tons), fortunately none of the men on these vessels were lost with the ships. All three were British registered ships, but the fourth ship involved was an American. The 1,571 ton sailing vessel Pass of Balmaha was en route to Russia when she was intercepted by HMS Victorian, upon inspection her master, Captain Scott, was ordered to take his ship to England for further inspection, he was also ordered to hoist the Union flag in place of the U.S. flag. This is why Gräff attacked the ship as he would not have attacked an American ship without provocation. When U-36 approached the Union flag was hauled down and the U.S. flag was run up, the British were hidden below, but Gräff, being somewhat suspicious of the whole ordeal, ordered the ship to Cuxhaven.

The British remained locked away until they arrived in Cuxhaven, where their existence was revealed by Captain Scott. Because they behaved honorably the American crew was released and sent to a neutral country, the British of course became prisoners, but the ship remained in Germany. There she was converted into a hilfskreuzer and renamed SMS Seeadler (Sea Eagle), her voyage is of course legendary.

The last ship to be stopped by Gräff was a Danish steamer named Louise, the Germans were about to board the ship when a British collier came into view, apparently preferring the British ship, Gräff left the Dane in pursuit of the Engländer. The unlucky ship was the Prince Charles, a 373 ton collier built in 1905. U-36 approached the ship and when she was within 600 yards fired on her, the ship stopped immediately and panic stricken men dashed about on the deck awaiting their fate.

The ship was indeed unlucky, but unlucky for the Germans, you see Prince Charles was a Q-ship, and her commander, Lt. William P. Mark-Wardlaw, R.N. and his crew were ready, the "panic stricken men" were part of the rouse to lure the unsuspecting submarine in close for the kill. As the two vessels moved closer together U-36 continued to fire, but the men behind the hidden guns on Prince Charles remained still, even with shells falling around them. When Gräff came to a stop and turned broadside to Prince Charles, Mark-Wardlaw ordered the camouflage hiding the guns to be dropped, the White Ensign to be hauled up and for his men to open fire.

As soon as Prince Charles opened fire the German gunners made for the conning tower to avoid being killed, the first shot missed, but in short order the gunners found the range and began to hit the boat. Men began to pour from the submarine, fifteen men, including Gräff, got out before she went down stern first, eighteen of their comrades were still inside. When U-36 disappeared beneath the waves she became the first enemy submarine sunk by a Q-ship without any other aid.

Mark-Wardlaw had proven that a ragged old ship could indeed best a U-boat, he was awarded the D.S.C. and by 1938 rose to the rank of Rear Admiral. Prince Charles was returned to civilian service and continued to sail under several different names until she capsized on Dec. 10, 1944.