United States Navy operations during World War I United States Navy operations during World War I began on April 6 , 1917 , after the formal declaration of war on Germany . The American navy focused on countering enemy U - boat s in the Atlantic Ocean and the Mediterranean Sea while convoying men and supplies to frontlines in France and Italy . Because of United States ' late entry into the war her capital ship s never engaged the Germans and few decisive submarine actions occurred . Operations . Atlantic Ocean . The main theater of World War I was the Western Front and in order to relieve the British and European allies already on the frontline , the United States Navy was tasked with transporting millions of American soldiers and supplies across the Atlantic to France as soon as possible . The United States Navy was ill prepared for war though ; the only solution was to begin deploying whatever was available on convoy duty and arming merchantmen with small naval gun s and armed guard detachments . The United States Coast Guard was also officially organized as part of the navy . Destroyer s and other similar warships of the escort type were thought to be the most effective means of sinking German submarines and protecting merchantmen so destroyer squadrons were based in the British Isles at ports such as Queenston , Ireland . The capital ships took up positions with the British Royal Navy in the North Sea for an uneventful blockade of the German High Seas Fleet that would last into 1919 . The first victory for the United States Navy during the war occurred on October 15 , 1917 , in the Atlantic . That day the destroyer , under Lieutenant Commander W . N . Vernon , encountered the " U - 61 " off Mind Head , Ireland in the Celtic Sea . After chasing the U - boat for about an hour it turned around and released a single torpedo which hit the " Cassin " aft on portside . Just before the explosion Gunner ' s Mate First Class Osmond Ingram noticed the torpedo and he alarmed the K - gun crew who began launching depth charge s at the Germans . A large portion of the ship was blown off but the Americans were able to keep her watertight while returning fire . Ingram was the only man killed in the battle and he received the Medal of Honor for his exceptional conduct . Nine others were wounded and the Americans won the day after striking " U - 61 " s conning tower and forcing her to disengage . On November 17 , 1917 , two destroyers became the first ships to sink an enemy submarine in United States history . and were escorting convoy OQ - 20 eastbound when a lookout sighted the periscope of " U - 58 " . In the subsequent action , the U - boat was forced to surface by depth charges and then defeated in a surface engagement . At least one shot from the " Nicholson " hit the German vessel , killing two men and causing heavy damage . Thirty eight survivors escaped the sinking " U - 58 " and they surrendered to the American commanders ; Lieutenant s Frank Berrien and Arthur S . Carpender , both of whom received the Navy Cross . Four United States Navy ships were lost during America ' s involvement in the conflict , only two by enemy action though six merchant ships with armed guards aboard were also destroyed . The first combat sinking was that of , a destroyer , which was sailing in a zig - zag pattern with five other warships back to Ireland from Brest . On December 17 , " Kapitänleutnant " Hans Rose of " U - 53 " sighted the " Jacob Jones " and attacked her with a spread of torpedoes , one of which was spotted by the Americans . Despite the ship taking evasive measures it was fatally damaged . Commander David W . Bagley ordered his crew to abandon ship and while the vessel was sinking the armed depth charges aboard began to detonate , adding to the already heavy casualties . Sixty - six American servicemen were killed and dozens more were wounded , only thirty - eight men survived . The " Jacob Jones " was the first American destroyer sunk in combat and she went down within eight minutes of being struck . Three United States Army and navy transports , USAT " Henry R . Mallory " , USAT " Tenadores " and received credit for defeating a U - boat on the morning of April 4 , 1918 . While sailing back to the United States from France at 11 : 45 , a German U - boat of unknown designation surfaced and fired torpedoes at " Mallory " . Lookouts aboard the transport spotted the tracks and the ship successfully evaded them . The submarine then came in sight and all three ships opened fire with their main guns , and hit the submarine as it submerged . The Americans then maneuvered in close and began dropping depth charges but that was the last they heard of the Germans . The auxiliary yacht engaged on May 21 the " UC - 56 " twice off the coast of Spain while escorting a British merchantman . That afternoon an oil slick was spotted by the " Christabel " s crew and later on the wake of the submarine . Depth charges were dropped but the Germans escaped , only to return and harass the convoy later that night . At about 11 : 00 pm lookouts on the " Cristabel " sighted the German ' s periscope and they immediately maneuvered to fire some more depth charges . Several successive hits damaged the U - boat but it escaped though it had to cruise on the surface to Santander in order to prevent sinking . In Spain the crew of " UC - 56 " were interned and the boat scuttled before it could be handed over . During the action a few depth charges went loose aboard the " Christabel " and at great personal risk , Ensign Daniel Augustus Joseph Sullivan secured the explosives , an act which later earned him the Medal of Honor . The British ocean liner was attacked on June 18 by " U - 151 " approximately 400 miles off the Bermudas . Twenty - two men went down with the ship and the rest made it into lifeboat s . The Germans remained in the area though for her commander decided to use the British as bait for any allies vessels coming to the rescue . A few hours later the auxiliary cruiser USS " Von Steuben " arrived in the area and she found the lifeboats . But before reaching them a torpedo was spotted in the water . Two guns were then opened up , one fired on the incoming torpedo and the other on " U - 151 " s periscope . The ship also began evasive maneuvers and the missile passed harmlessly by . " U - 156 " , under Richard Feldt , raided the port of Orleans , Massachusetts , on the morning of July 18 . The Germans surfaced while it was still dark and positioned their ship off Nauset Beach to begin bombarding the civilian tugboat and four wooden barges . In a short time all five craft were on fire and sinking . A few shells missed their targets and landed , becoming the first enemy shells to fall on continental United States territory since the 1846 Siege of Fort Texas during the Mexican War . Just as Commander Feldt was planning to submerge and leave the area , nine Coast Guard Curtiss HS seaplane s counterattacked by dropping bombs but they failed to detonate and the Germans left unharmed . On the following day , July 19 , USS " San Diego " suffered an explosion while heading from Portsmouth Naval Yard to New York . The armored cruiser was northeast of Fire Island when a suspected torpedo hit portside at the engine room below the waterline . Damage prevented a water tight hatch from sealing properly and both the engine room and fire room No . 9 flooded in minutes . Captain Harley H . Christy believed he was under attack by a submarine so he ordered his men to battle stations and they began shooting at anything that resembled a periscope . When it became apparent that the ship could not be saved , the captain and the survivors abandoned ship . Twenty - eight minutes after the explosion the " San Diego " was underwater , taking down six men with her . There was some controversy as to what actually caused the sinking though eventually sea mine s from " U - 156 " were attributed to the incident . USS " San Diego " was the only American capital ship lost in the war . The only lightvessel of the United States destroyed in combat was the Diamond Shoal Lightship No . 71 . On August 6 , " LV - 71 " was patrolling off North Carolina ' s Diamond Shoals when she came across the sinking American cargo ship , a victim of the submarine " U - 140 " . Survivors were taken on board and " LV - 71 " s commander , Master Walter Barnett , sent out a warning to friendly ships in the area that a U - boat was near . The Germans intercepted the signal so they raced back to the wreck of the " Merak " . Upon arrival , " U - 140 " surfaced and Commander Waldemar Kophamel demanded that the Americans evacuate the lightship . " LV - 71 " was unarmed so Master Barnett had no choice but to row ashore in a dinghy while the Germans sank his ship with deck gunfire . There were no casualties in the incident on either side . USS " Mount Vernon " was a former German ocean liner which was taken over by the United States Navy and armed . On the morning of September 5 , 1918 , the " Mount Vernon " was off the coast of France with four destroyers when the periscope of " U - 82 " was sighted . " Mount Vernon " then engaged with her main guns and hit the submarine which in turn fired a torpedo . The Americans tried to avoid the incoming threat but it could not be done and the torpedo hit . Thirty - six men were killed and thirteen wounded out of almost 1 , 500 on board but the ship was saved . , , and USS " Nicholson " dropped depth charges for several minutes but the U - boat got away . North Sea . With the encouragement of Assistant Secretary of the Navy Franklin D . Roosevelt , the United States manufactured 100 , 000 naval mine s for the North Sea Mine Barrage to prevent U - boats from reaching Atlantic shipping lanes . The United States North Sea Mine Force commanded by Rear Admiral Joseph Strauss aboard the Atlantic Fleet Mine Force flagship USS laid the new type of mine in deeper water than had ever before been mined . Rear Admiral Lewis Clinton - Baker , commanding the Royal Navy minelaying force at the time , described the barrage as the " biggest mine planting stunt in the world ' s history . " The official statistics on lost German submarines compiled on 1 March 1919 credited the North Sea mine barrage with the certain destruction of four U - boats , probable destruction of two more , and possible destruction of another two . Mediterranean Sea . American naval operations in the Mediterranean took the form of escorting convoys and delivering supplies . The Mediterranean was not without enemies , Austro - Hungarian forces in northern Italy and the Ottoman Empire were two major threats though by 1917 their navies were mostly defeated or blockaded by ships of the Otranto Barrage . Other than the land Battle of Vittorio Veneto , the Americans engaged in only two memorable battles in the Mediterranean theater . The first was when together with sank a U - boat off Algiers on May 8 , 1918 . " Lydonia " and " Basilisk " were steaming with a convoy from Bizerte to Gibraltar when they came across the German submarine . A coordinated depth charge attack ensued but the Germans were able to torpedo the British merchant ship , which sank . After a fifteen - minute running battle , the depth charging was stopped and survivors of the " Ingleside " were rescued . Heavy seas prevented an immediate assessment of possible damage to the submarine but later evaluations credited USS " Lydonia " and HMS " Basilisk " with sinking " UB - 70 " when she failed to show up at any port . Twelve American submarine chaser s under Captain Charles P . Nelson were part of attack on the Austro - Hungarian held naval base at Durazzo , Albania . The battle began on October 11 with Italian and British aircraft bombarding Austro - Hungarian concentrations within the city while the allied fleet was still crossing the Adriatic Sea . When they arrived , the larger ships engaged shore batteries while the Americans plotted a path through a sea mine field and engaged two Austro - Hungarian submarines , and . Two destroyers and a torpedo boat were also damaged by American and British ships with help from some Italian MAS boats and one merchant vessel was sunk . In the end no Americans were hurt in the battle and the naval base was left in ruins . For his leadership and courage at Durrazo Captain Nelson received the Navy Distinguished Service Medal as well as other foreign decorations . Coast Guard Captain Leroy Reinburg of the engaged enemy submarines near the Strait of Gibraltar in November 1918 . The " Druid " was operating as part of the Gibraltar Barrage , a squadron of American and British ships assigned to keeping enemy U - boats from passing from the Mediterranean into the Atlantic . On November 8 , 1918 , men on board USS " Druid " sighted three surfaced submarines going through the strait . The weather was foul and the seas rough but the barrage squadron attacked anyway , first with gunfire and then with depth charges . reported that she shot a hole through one of the submarines ' conning towers with a gun but other than that no other damage was thought to have occurred . USS " Druid " and her compatriots were successful in defending the strait and on the following day the Americans helped rescue the British crew of the battleship which had been torpedoed by " UB - 50 " while passing through Gibraltar into the Mediterranean . The war ended three days later on November 11 . Pacific Ocean . American naval forces in the Pacific Theater of World War I were far removed from the conflict with Germany and the other Central Powers . Though the Germans had possessed colonies at the beginning of the war , by 1917 all of them had been conquered by the allies . The only significant United States naval presence in the Pacific was a cruiser squadron under Admiral Austin M . Knight . There was only one engagement in the theater involving the United States and it began the day after war was declared . In December 1914 the German auxiliary cruiser was commerce raiding in the South Pacific when her commander decided he needed provisions so he put in for the neutral island of Guam , a United States territory . Captain Adalbert Zuckschwerdt asked the Americans for coal but there was little on the island and without enough to leave the Germans were interned for three years . When the war finally did break out on April 6 , 1917 , the old schooner was ordered to demand the " Cormoran " s surrender or sink her if the crew failed to cooperate . Captain Zuckschwerdt had no intention of handing his vessel over to the Americans so he ordered his men to scuttle the ship . This was unacceptable to the men of USS " Supply " so the marines on board fired America ' s first war time shots with rifles . Nine Germans were killed that day either by the rifle fire or by the large explosion which sank the " Cormoran " .