ORIGINAL: Capt Cliff
INJ sub tactics were in support of the fleet unlike USN and the German Navy sub tactic that were directed against shipping/commerce. Sure they sunk the occasional ship they came across but for them to camp out along the west coast is a bit much. IMHO. So 180 ships for the entire war?
My "ships sunk by I-boat" list is probably incomplete, but here are 3 first months. Quite a many "occasional" ships, I think... Warships (like CV Saratoga and K-XVI) are missing from that list.
7th Dec 1941: I-26 sink US cargo ship Cynthia Olson, Eastern Pacific
10th Dec 1941: I-10 sink Panamian cargo ship Donerail, near Hawaii
10th Dec 1941: I-124 sink british cargo ship Hereldawins, near Luzon
11th Dec 1941: I-156 sink norwegian cargo ship Hai Tung, near Singapore?
12th Dec 1941: I-9 sink US cargo ship Lahaina, near Hawaii
14th Dec 1941: I-4 sink norwegian cargo ship Hoeg Merchant, near Hawaii
17th Dec 1941: I-175 sink Us cargo ship Manini, near Hawaii
19th Dec 1941: I-172 sink US cagro ship Prusa, near Hawaii
22nd Dec 1941: I-17 damage US tanker Emidio, West Coast of US
23th Dec 1941: I-17 damage US tanker Doheny, West coast of US
23rd Dec 1941: I-21 sink US tanker Mentebello, West Coast of US
23rd Dec 1941: I-21 damage US tanker Idaho, West Coast of US
24th Dec 1942: I-23 damage US Cargo ship Dorothy Phillips, West Coast of US
25th Dec 1941: I-19 damage US cargo ship Absoroka, West Coast of US
27th Dec 1941: I-25 damage US tanker Connecticut, West Coast of US
3th Jan 1942: I-158 sink dutch cargo ship Langkoeas, Java Sea
5th Jan 1942: I-156 sink british cargo ship Kwangtung, Indian Ocean
7th Jan 1942: I-156 sink dutch cargo ship Van Rees, South of Java
7th Jan 1942: I-157 sink dutch cargo ship Djirak, Bali Sea
8th Jan 1942: I-156 sink dutch cargo ship Van Riebeeck, South of Java
9th Jan 1942: I-156 sink dutch cargo ship Camphuys, Java Sea
9th Jan 1942: I-165 sink dutch cargo ship Bankoelen, Java Sea
11th Jan 1942: I-166 sink US cargo ship Liberty Glo, Java Sea
12th Jan 1942: I-156 damage dutch cargo ship Patras, near Bali
14th Jan 1942: I-165 sink british cargo ship Jalarajan, Indian Ocean
20th Jan 1942: I-159 sink norwegian cargo ship Eidsvold, Indian Ocean
21st Jan 1942: I-166 sink panamian cagro ship Nord, Andaman Sea
22nd Jan 1942: I-166 sink british cargo ship Chak Sang, Bay of Bengal
23rd Jan 1942: I-172 sink USN Oiler Neches, near Hawaii
25th Jan 1942: I-159 sink british cargo ship Giang Sen(?), Indian Ocean
28th Jan 1942: I-64 damage british cargo ship Idar, Indian Ocean
29th Jan 1942: I-64 sink US cargo ship Florence Luckenbach, Indian Ocean
29th Jan 1942: I-171 sink US small cargo ship General Royal T. Frank, near Hawaii
30th Jan 1942: I-64 sink Indian cargo ship Jalatarang, Indian Ocean
31st Jan 1942: I-64 sink Indian cango ship Jalapalaka, Indian Ocean
31st Jan 1942: I-162 damage british tanker Longwood, near Ceylon
3rd Feb 1942: I-162 damage british tanker Spondilius, near Ceylon
4th Feb 1942: I-156 sink dutch cargo ship Togian, Indian Ocean
7th Feb 1942: I-153 sink unidentified cargo ship, south of Java
7th Feb 1942: I-155 sink dutch passenger ship(?) Van Cloon, Java Sea
9th Feb 1942: I-165 damage british cargo ship Laomedon, Indian Ocean
13th Feb 1942: I-155 sink british cargo ship Derrymore, Java Sea
14th Feb 1942: I-166 sink british cargo ship Kamuning, Indian Ocean
15th Feb 1942: I-165 sink danish cagro ship Johanne Justen, Indian Ocean
20th Feb 1942: I-165 sink british cargo ship Bhima, Indian Ocean
22nd Feb 1942: I-158 sink dutch passenger ship Pijnacker Hordijk, Java Sea
25th Feb 1942: I-158 sink dutch cargo ship Boeroe, Java Sea
27th Feb 1942: I-153 sink dutch cargo ship Moesi, Java Sea
28th Feb 1942: I-153 sink birtish cargo ship City of Manchester, Indian Ocean?
28th Feb 1942: I-158 damage british tanker British Justice, Java Sea
28th Feb 1942: I-2 sink british cargo ship Nam Youg in Indian Ocean
28th Feb 1942: I-4 sink singaporean cargo ship Ban Ho Guan in Indian Ocean
EDIT: That's 41 ships glugluglu in less than 3 months. I wonder how many JFB can do the same?
Many I-boats operated West Coast of US. Last ships they sunk were US tanker Larry Doheny (6th Oct 1942) and missidentified Soviet minelayer L-16 (11th Oct 1942). I-25 sunk both of them.
Most successful I-boat was probably I-10. That one got 15 "kills", 13 cargo ships and 2 tankers. At least I-21, I-26 and I-27 sunk 10 ships or more.