The 1917 Battle of the Strait of Otranto was the result of an
Austro-Hungarian raid on the Otranto Barrage, an Allied naval
blockade of the Strait of Otranto. The battle took place over
14–15 May 1917, and was the largest surface action in the
Adriatic Sea during World War I. The Otranto Barrage was a fixed
barrier, composed of lightly armed drifters with anti-submarine
nets coupled with minefields and supported by Allied naval
patrols.
The Austro-Hungarian navy planned to raid the Otranto Barrage with
a force of three light cruisers and two destroyers under the
command of Captain Miklós Horthy, in an attempt to break the
barrier to allow U-boats freer access to the Mediterranean, and
Allied shipping. An Allied force composed of ships from three
navies responded to the raid and in the ensuing battle, heavily
damaged the Austro-Hungarian cruiser SMS Novara. However, the rapid
approach of the Austro-Hungarian relief force persuaded Rear
Admiral Acton, the Allied commander, to retreat.
Disposition of forces
Under the command of Horthy, three Austro-Hungarian cruisers:
Novara, Saida, and Helgoland, modified to resemble large British
destroyers, were to attack the drifters on the night of 14 May and
attempt to destroy as many as possible before daybreak. The
destroyers Csepel and Balaton were to mount a diversionary raid off
the Albanian coast in order to confuse any Allied counter-attack.
Two Austro-Hungarian U-boats, U-4 and U-27, along with the German
U-boat UC-25, were to participate in the operation as well. A
supporting force composed of the armored cruiser Sankt Georg, two
destroyers, and a number of torpedo boats was on standby if the
raiders ran into trouble. The old pre-dreadnought battleship
Budapest and a screen of torpedo boats were also available if
necessary.
An Allied destroyer patrol was in the area on the night of 14 May,
to the north of the Barrage. The Italian flotilla leader Mirabello
was accompanied by the French destroyers Commandant Rivière,
Bisson, and Cimeterre. The Italian destroyer Borea was also in the
area, escorting a small convoy to Valona. A support force was based
in the port of Brindisi, consisting of the British cruisers
Dartmouth and Bristol and several French and Italian
destroyers.
Raid on the drifters
The Italian convoy escorted by Borea was attacked by the
Austro-Hungarian destroyers Csepel and Balaton at approximately
03:24. The Austro-Hungarians sank the Borea and a munitions ship,
and a second was set on fire and abandoned.
The three cruisers were able to pass through the line of drifters,
and at 03:30 began attacking the small barrage ships. The
Austro-Hungarians frequently gave the drifter crews warning to
abandon ship before opening fire. In some instances, the drifter
crews chose to fight: the Gowan Lee returned fire on the
Austo-Hungarian ships. The ship was heavily damaged, but remained
afloat; her captain, Joseph Watt, was later awarded the Victoria
Cross for his actions during the battle.
There were 47 drifters in Barrage on the night of 14 May; the
Austro-Hungarians managed to sink 14 drifters and damage 4 more.
The lack of sufficient Allied escorts forced the withdrawal of the
remaining blockading ships, although only for a short time.
Battle
By this time, the Allied naval forces in the area were aware of
the raid, and were in a position to block the Austro-Hungarian
retreat. Rear Admiral Alfredo Acton, the commanding officer of the
Italian Scouting Division, ordered the Mirabello's group southward
at 04:35, while he embarked on the British light cruiser HMS
Dartmouth. By 06:45, the cruisers Dartmouth and HMS Bristol, along
with the Italian destroyers Mosto, Pilo, Schiaffino, Acerbi, and
Aquila were sailing north in an attempt to cut off the
Austro-Hungarian cruisers. The Italian light cruiser Marsala, the
flotilla leader Racchia, and the destroyers Insidioso, Indomito,
and Impavido were readying to sail in support as well.
The Mirabello group engaged the Austro-Hungarian cruisers at 07:00,
but were heavily outgunned, and instead attempted to shadow the
fleeing cruisers. At 07:45, Rear Admiral Acton's ships encountered
the destroyers Csepel and Balaton. After 20 minutes, the Italian
destroyers were able to close the distance to the Austro-Hungarian
ships; the two groups engaged in a short artillery duel before a
shot from Csepel struck Aquila and disabled the ship's boilers. By
this time, the Austro-Hungarian destroyers were under the cover of
the coastal batteries at Durazzo, and were able to make good their
escape.
At 09:00, Bristol's lookouts spotted the smoke from the
Austro-Hungarian cruisers to the south of her position. The Allied
ships turned to engage the Austro-Hungarian ships; the British
ships had both a superiority in numbers and in firepower; Dartmouth
was armed with eight 6 in (150 mm) guns and Bristol had two 6 inch
and ten 4 in (100 mm), compared to the nine 3.9 in (99 mm) guns on
each of the Austro-Hungarian ships. Unfortunately for the Allies,
their numerical superiority was quickly lost, as their destroyers
were either occupied with mechanical problems, or protecting those
destroyers suffering from breakdowns. The support forces of both
sides—the Sankt Georg group for the Austro-Hungarians, and
the Marsala group for the Allies—were quickly dispatched to
the battle.
The Dartmouth, faster than Bristol, closed to effective engagement
range with the Austro-Hungarian ships, and opened fire. A shell
from Dartmouth struck the Novara, at which point the
Austro-Hungarian ships laid a smoke screen in order to close the
distance. Dartmouth was struck several times, and by 11:00, Acton
ordered the ship to reduce speed to allow Bristol to catch up.
Novara was hit several more times, and her main feed pumps and
starboard auxiliary steam pipe had been damaged, which caused the
ship to begin losing speed. At 11:05, Acton turned away in an
attempt to separate the Saida from the Novara and Helgoland. At
this point, the Sankt Georg was approaching the scene, which
prompted Acton to temporarily withdraw to consolidate his forces.
This break in the action was enough time for the Austro-Hungarians
to save the crippled Novara; Saida took the ship under tow while
Helgoland covered them.
Unaware that the Novara had been disabled, and fearing that his
ships would be drawn too close to the Austrian naval base at
Cattaro, Acton broke off the pursuit. The destroyer Acerbi misread
the signal, and attempted to launch a torpedo attack, but was
driven off by the combined fire of the Novara, Saida, and
Helgoland. At 12:05, Acton realized the dire situation Novara was
in, but by this time, the Sankt Georg group was too close. The
Sankt Georg group rendezvoused with the Novara, Saida, and
Helgoland, and the Csepel and Balaton reached the scene as well.
The entire group returned to Cattaro together.
At 13:30, the submarine UC-25 torpedoed the Dartmouth, causing
serious damage. The escorting destroyers forced UC-25 from the
area, but the Dartmouth had to be abandoned for a period of time,
before it could be towed back to port. The French destroyer
Boutefeu attempted to pursue the German submarine, but struck a
mine laid by UC-25 that morning and sank rapidly.
Aftermath
As a result of the raid, it was decided by the British naval
command that unless sufficient destroyers were available to protect
the barrage, the drifters would have to be withdrawn at night. The
drifters would only be operating for less than twelve hours a day,
and would have to leave their positions by 15:00 every day. Despite
the damage received by the Austro-Hungarian cruisers during the
pursuit by Dartmouth and Bristol, the Austro-Hungarian forces
inflicted more serious casualties on the Allied blockade. In
addition to the sunk and damaged drifters, the cruiser Dartmouth
was nearly sunk by the German submarine UC-25, the destroyer
Boutefeu was mined and sunk, and a munitions convoy to Valona was
interdicted.
However, in a strategic sense, the battle had little impact on the
war. The barrage was never particularly effective at preventing the
U-boat operations of Germany and Austria-Hungary in the first
place. The drifters could cover approximately .5 mi (0.80 km)
apiece; of the 40 mi (64 km)-wide Strait, only slightly more than
half was covered. The raid risked some of the most advanced units
of the Austro-Hungarian fleet on an operation that offered minimal
strategic returns.
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