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U5 submarines (1910-1911)


U5 1915


Name No Yard No Builder Laid down Launched Comp Fate
U5     Whitehead, Fiume 4/1908 10.2.1909 4/1910 to Italy 1920
U6     Whitehead, Fiume 2/1908 12.9.1909 7/1910 sunk 10.5.1916
U12 (ex-U7, ex-SS3)     Whitehead, Fiume 1910 14.3.1911 1911 // 8.1914 sunk 12.8.1916

Technical data

Displacement normal, t

U5, 6: 236 / 273

U12: 240 / 270

Displacement full, t


Length, m


Breadth, m


Draught, m


No of shafts



2 petrol engines / 2 electric motors

Power, h. p.

U5, 6: 400 / 230

U12: 400 / 220

Max speed, kts

U5, 6: 10.1 / 9

U12: 10 / 8

Fuel, t


Endurance, nm(kts)

2500(7) / 60(3)


2 - 450 TT (bow, 4)


U5, 6: 19

U12: 17

Diving depth operational, m


Standard scale images

<i>U5 </i>1914
U5 1914
<i>U12 </i>1915
U12 1915


<i>U5 </i>1915
U5 1915
<i>U6 </i>1916
U6 1916

Project history

These boats were built by the Fiume-based firm of Whitehead which had bought a license from the Irish-American John Philip Holland to build his submarines. The first two boats were partially assembled in the United States and assembled at Whitehead's, which caused a lot of trouble. The third boat was built on speculation and featured improvements in all the mechanical and electrical systems. Named S.S.3 this unit was offered to the Austrian Navy too, but she was refused because the trials programme was not yet completed. Whitehead then offered the boat to the navies of Peru, Portugal, Netherlands, Brazil, Bulgaria and again to the Austro-Hungarian Navy. When war broke out Austria bought the unsold boat and provisionally commissioned her as U7, but by the end of August 1914 she was definitely commissioned as U12. The single-hulled Holland type featured a distinctive tear-drop hull and an interesting design of the TT hatches: these were clover-leaf shaped and rotated on a central axis.

Modernizations 11.

1914, U5; 12.1914, U12, 12.1915, U6: + 1 x 1 - 37/20 SFK L/23 H

early 1915, U12: petrol engines were replaced by diesels (600hp)

1917, U5: - 1 x 1 - 37/20; + 1 x 1 - 75/27 G. L/30 K.16 BAG

Naval service

All three saw active war service. U5, sunk after hitting a mine during trials on 16 May 1917, was raised and rebuilt with a conning tower and a 7.5cm/30 gun; she was ceded as a war reparation to Italy in 1920 and scrapped. U6 was trapped in submarine nets during an attempt to break through the Otranto barrage and scuttled by the crew 10.5.1916. U12 was sunk with the loss of all hands by a mine when trying to penetrate the harbour of Venice, about 12 August 1916. Raised by Italy at the end of 1916 she was scrapped in the Venice N Yd.