SM UC-21 explained

SM UC-21 was a German Type UC II minelaying submarine or U-boat in the German Imperial Navy (German: Kaiserliche Marine) during World War I. The U-boat was ordered on 29 August 1915 and was launched on 1 April 1916. She was commissioned into the German Imperial Navy on 12 September 1916 as SM UC-21.[1]

In eleven patrols UC-21 was credited with sinking 98 ships, either by torpedo or by mines laid. They included the British hospital ship, which UC-21 torpedoed in the English Channel on 17 April 1917, killing 29 already wounded soldiers and 12 crew.[2]

UC-21 disappeared after departing Zeebrugge for the Bay of Biscay on 13 September 1917.

Design

Like all pre-UC-25 Type UC II submarines, UC-21 had a displacement of 417t when at the surface and 493t while submerged. She had a total length of 49.35m (161.91feet), a beam of 5.22m (17.13feet), and a draught of 3.650NaN0. The submarine was powered by two six-cylinder four-stroke diesel engines each producing 250PS (a total of 500PS), two electric motors producing 460PS, and two propeller shafts. She had a dive time of 35 seconds and was capable of operating at a depth of .

The submarine had a maximum surface speed of and a submerged speed of . When submerged, she could operate for at ; when surfaced, she could travel at . UC-21 was fitted with six mine tubes, eighteen UC 200 mines, three torpedo tubes (one on the stern and two on the bow), seven torpedoes, and one 8.8sp=usNaNsp=us Uk L/30 deck gun. Her complement was twenty-six crew members.

Summary of raiding history

DateNameNationalityTonnage[3] Fate[4]
28 November 1916Clematis United Kingdom22Sunk
28 November 1916Lady of the Lake United Kingdom91Sunk
28 November 1916Vulcan United Kingdom27Sunk
28 November 1916HMD Pelagia84Sunk
30 November 1916Draupner Norway1,126Sunk
30 November 1916Eggesford United Kingdom4,414Damaged
30 November 1916Therese France165Sunk
1 December 1916King Bleddyn United Kingdom4,387Sunk
2 December 1916Demetrios Inglesis Greece2,088Sunk
2 December 1916Robinson France186Sunk
2 December 1916Uribitarte Spain1,756Sunk
3 December 1916Aiglon France280Sunk
3 December 1916Louise France155Sunk
3 December 1916Verdun France184Sunk
4 December 1916Pallas1,202Sunk
5 December 1916Nexos Denmark1,013Sunk
6 December 1916Gerona Spain1,328Sunk
7 December 1916Avristan United Kingdom3,818Sunk
8 December 1916HMT Dagon250Sunk
8 December 1916Falk Norway1,379Sunk
8 December 1916Marjolaine France163Sunk
8 December 1916Modum Norway2,937Sunk
17 December 1916Margaret United Kingdom54Sunk
18 January 1917778Damaged
19 January 1917Joseph Rosalie France138Sunk
19 January 1917Marietta Di Giorgio Norway988Sunk
19 January 1917Tremeadow United Kingdom3,653Sunk
20 January 1917Kisagata Maru No. 3 Japan2,588Sunk
20 January 1917Jotunfjell Norway2,492Damaged
21 January 1917Victoire France290Damaged
21 January 1917Leontine France124Sunk
21 January 1917Saint Pierre France127Sunk
22 January 1917Bearnais France301Sunk
22 January 1917Precurseur France364Sunk
22 January 1917Steinmachos Greece1,175Sunk
24 January 1917Dan Denmark1,869Sunk
24 January 1917Gladiateur France23Sunk
24 January 1917Loire III France27Sunk
24 January 1917Marie 3 France25Sunk
24 January 1917Quebec France3,346Sunk
24 January 1917Vega Denmark195Sunk
25 January 1917Myrdal Norway2,631Sunk
1 February 1917Sainte Helene France2,128Sunk
10 February 1917Beechtree United Kingdom1,277Sunk
11 February 1917Dernes Norway738Sunk
12 February 1917Nordcap Norway332Sunk
13 February 1917Progreso Norway1,620Sunk
14 February 1917Longscar United Kingdom2,777Sunk
14 February 1917Mar Adriatico Spain2,410Sunk
15 February 1917Aline France30Sunk
15 February 1917Marion Dawson United Kingdom2,300Sunk
16 February 1917Niobe France1,319Sunk
16 February 1917Pollcrea United Kingdom1,209Damaged
17 February 1917Cabo Norway1,254Sunk
17 February 1917Silene France171Sunk
18 February 1917Triumph United Kingdom52Sunk
19 February 1917Rutenfjell Norway1,844Sunk
10 March 1917Asbjørn Norway3,459Sunk
12 March 1917Alice Charles France41Sunk
12 March 1917Arethuse France40Sunk
13 March 1917Girda Norway1,824Sunk
13 March 1917Vivina Spain3,034Sunk
14 March 1917Blaamanden Norway954Sunk
14 March 1917La Marne France133Sunk
15 March 1917Eugene Robert France98Sunk
15 March 1917Fleur D’Esperance France24Sunk
15 March 1917Frimaire United Kingdom1,778Sunk
15 March 1917Petit Jean France21Sunk
16 March 1917Anais France130Sunk
16 March 1917Madeleine Davoust France148Sunk
16 March 1917Ronald Norway3,021Sunk
18 March 1917Illinois United States5,225Sunk
17 April 1917HMHS Donegal1,885Sunk
19 April 1917Cilurnum United Kingdom3,126Sunk
20 April 1917Georgios Greece3,124Sunk
21 April 1917Emile Et Charlotte France41Sunk
21 April 1917Ville De Dieppe Norway1,254Sunk
22 April 1917Capenor United Kingdom2,536Sunk
22 April 1917Percy Birdsall United States1,127Sunk
22 April 1917Valerie Norway2,140Sunk
24 April 1917Barnton United Kingdom1,858Sunk
25 April 1917Baigorry France2,161Sunk
26 April 1917Boy Denis United Kingdom41Sunk
22 May 1917Jeune Albert France25Sunk
23 May 1917Harwood Palmer United States2,885Sunk
23 May 1917Lesto United Kingdom1,940Sunk
26 May 1917Aristides Greece2,179Sunk
26 May 1917Norhaug Norway1,245Sunk
27 May 1917Efstathios Greece3,847Sunk
28 May 1917Hiram Norway598Sunk
28 May 1917Urna Norway2,686Sunk
28 May 1917Waldemar Norway1,267Sunk
30 May 1917Sørland Norway2,472Sunk
2 June 1917Tonawanda United Kingdom3,421Damaged
7 June 1917Hafnia Denmark1,619Sunk
29 June 1917Lauwerzee Netherlands47Sunk
4 July 1917Bestevaer Netherlands1,044Sunk
4 July 1917Roelfina Netherlands148Captured as prize
11 July 1917Coquimbo France1,759Sunk
15 August 1917Phoebe France3,956Sunk
17 August 1917Pontoporos Greece4,049Sunk
19 August 1917Therese & Marie France1,615Sunk
31 August 1917Marques De Mudela Spain1,930Sunk
16 September 1917Ann J. Trainer United States426Sunk
23 September 1917St. Dunstan United Kingdom730Sunk

Bibliography

Notes and References

  1. "SM" stands for "Seiner Majestät" (English: His Majesty's) and combined with the U for Unterseeboot translates as His Majesty's Submarine.
  2. Book: 1918 . The War on Hospital Ships, With Narratives of Eye-Witnesses and British and German Diplomatic Correspondence . Second and Revised . New York and London . . 16.
  3. Merchant ship tonnages are in gross register tons. Military vessels are listed by tons displacement.
  4. uc21. UC 21. 1boat. 12 December 2014.

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