© April 1999 Anthony P. Tully

© 2018 Revision Anthony P. Tully

1940

25 May 1940:
Surgeon Lt Uchiyama resumes full-time duty aboard MIZUHO.

1 June 1940:
At Yokosuka, assigned directly to Combined Fleet.

7 October 1940:
Operations Officer LtCdr Maeda is reassigned. The position of Operations Officer remains vacant.

15 October 1940:
Captain (later RADM) Sumikawa Michio (45) (former Chief Equipping Officer, SHOKAKU) is appointed CO. Captain Hoshi is reassigned.
Cdr (later Captain) Yamaya Taro (48) (former Gunnery Officer, TAMA) is appointed XO. Cdr Sadohara is reassigned.
LtCdr (later Cdr) Cho Susumu (55) (former Navigator, TAMA) is appointed Navigator. LtCdr Kano is reassigned.
LtCdr (Eng.) (later Cdr) Tamekuni Jiro (Eng. 35) (former Division Officer, MUTSU) is appointed Maintenance Officer. LtCdr (Eng.) Mikumo is reassigned.

1 November 1940:
Lt/S (later LtCdr/S) Iwabuchi Tatsuo (1929) (former Surgeon, NOTORO) is appointed Surgeon. Lt/S Uchiyama is reassigned.
LtCdr (later Cdr) Ogasawara Shoichi (51) (former Air Officer, CHITOSE) is appointed Air Officer. LtCdr Hasegawa is reassigned.

15 November 1940:
Became flagship of RADM (later VADM) Kawase Shiro (38) (former ComDesRon 1)’s SeaplaTenDiv 7 (Seaplane Tender Division).
Special Duty LtCdr Suzuki Mioji is appointed Gunnery Officer. LtCdr Asano is reassigned.
Cdr (Eng.) (later Captain) Sakao Mitsutaro (Eng. 30) (former Chief Engineer, SubDiv 24) is appointed Chief Engineer. Cdr (Eng.) Gunjima is reassigned.
Lt/P (later LtCdr/P) Sendo Morizo (1938) is appointed Paymaster. Lt/P Ito is reassigned. Lt (Cdr posthumously) Fujioka Kenji (62) (former Navigator, SHIOKAZE) is appointed Communications Officer. LtCdr Yoshii is reassigned.

2 December 1940:
Flag of Seaplatendiv 7 removed; remainder of year spent under tactical command of CinC China Area Fleet.

1941

March 1941:
Reassigned to Seaplatendiv 11. In Inland Sea and Empire waters around Kyushu all the way till October.

10 April 1941:
Reassigned to RADM Kawase’s newly-activated SeaplaTenDiv 11. In Inland Sea and Empire waters around Kyushu till October.

15 August 1941:
Cdr (later Captain) Nito Jinnosuke (49) (former XO of KITAKAMI) is appointed XO. Cdr Yamaya is reassigned.

20 August 1941:
Lt (Cdr posthumously) Kitajima Takeshi (58) (former Navigator, WAKABA) is appointed Navigator. LtCdr Cho is appointed Navigator of HIRYU.
Cdr (Eng.) (Captain (Eng.) posthumously) Motohashi Seiichi (Eng. 31) (former Damage Control Officer, TAIGEI) is appointed Chief Engineer. Cdr (Eng.) Sakao is appointed an Equipping Officer of RYUHO.

1 September 1941:
RADM (later VADM) Fujita Ruitaro (38) (former ComDesRon 3) is appointed ComSeaplaTenDiv 11. RADM Kawase is appointed Director of the Torpedo School.
LtCdr (Eng.) (later Cdr) Tanaka Seiichi (Eng. 36) is appointed Maintenance Officer.
LtCdr (Eng.) Tamekuni is reassigned.
Lt (later LtCdr) Nagai Koji (62) (former Communications Officer, KAMOI) is appointed Communications Officer. Lt Fujioka is reassigned.

5 September 1941:
Captain (later RADM) Okuma Yuzuru (44) (former XO of HOSHO) is appointed CO. Captain Sumikawa is appointed Chief of the Air Technology Arsenal’s Administration Bureau.
Lt (Eng.) (Cdr posthumously) Azuma Masanori (Eng. 41) (former Chief Engineer, WAKABA) is appointed Damage Control Officer. Lt (Eng.) Yoshino is appointed Damage Control Officer of SORYU.

20 September 1941:
Lt/S (later LtCdr/S) Konaka Yukinari (1935) is appointed Surgeon. Lt/S Iwabuchi is reassigned.
Lt (j.g.)/P Nagami Shoji (1940) is appointed Paymaster. Lt/P Sendo is appointed Paymaster of RYUJO.

1 October 1941:
Cdr (Captain posthumously) Iwao Masatsugu (51) (former Air Officer, KIRISHIMA) is appointed Air Officer. LtCdr Ogasawara is reassigned.

15 October 1941:
Navigator Lt Kitajima is promoted LtCdr. Paymaster Lt (j.g.) Nagami is promoted Lt/P.

6 November 1941:
Assigned to Southern Force, Philippines Force, South Philippines Support Force Seaplane Force.

18 November 1941:
Depart Kitsuki for Kure, arrive Kure the next day.

24 November 1941:
Depart Kure, operate in Terashima Channel.

27 November 1941:
Depart for Palau in the Mandated Islands.

8 December 1941:
Depart Palau for Legaspi surprise attack operations.

15 December 1941:
Assigned to #2 Seaplane Force of Southern Force, Philippines Force.

12 - 16 December 1941:
At Cabugao Bay. Same assignment.

17 - 26 December 1941:
Assigned to Ramon Bay landing operations.

24 December 1941:
Arrive Anibawan Bay.

26 December 1941:
Assigned to #2 Air Force of Dutch East Indies Force, Eastern Occupation Force. Depart ed Lamon Bay for Palau.

29 December 1941:
Arrive at Palau.

31 December 1941:
Depart Palau for East Indies Operations.

1942

4 January:
Assigned to Seaplatendiv 11 with CHITOSE, which is the flagship of RADM Fujita Ruitaro 2nd Air Unit. Both tenders are anchored at Malalag Bay on the west side of Davao Gulf.
Action:
- 1155 Eight enemy B-17 bombers fly in from the northwest, bombing Japanese warships lined up, including MIZUHO. The tender is not hit, but cruiser MYOKO - flagship of Crudiv 5 - is struck forward and damaged. Comcrudiv 5 had to shift flag to NACHI and the MYOKO departed for repairs. [1]

9 January 1942:
Departed Malalag Bay to rendezvous with CHITOSE out of Pakiputan Strait to participate in the operations to occupy Menado.

10 January:
0900: MIZUHO and CHITOSE anchored at a point to the west of the Sangihe Islands. While there they carry out operations guarding the Menado Convoy, recon flights, and a harrassing bombing raid on an enemy radiotelephone station. After sunset departed and sailed on toward Menado.

11 January 1942:
0540: Arrived at Bangka anchorage. The two tenders carry out defense operations and support for the land actions from 0630 to 1900 using a total of forty-nine Jake seaplanes. Their aircraft engaged nine enemy flying boats and and four bombers, claiming two of the former shot down. In return, Seaplatendvi 11 lost three Jakes (one crashed, two lost after emergency landings) and other aircraft damaged. However, in a notable friendly-fire incident, a Jake of MIZUHO shot down a Japanese Type 96 transport of paratroopers of the 1001 Unit that crossed low over the anchorage and failed to give friendly indicators.

12-19 January:
Continued as before. No land support launches are necessary as resistance on Menado was light. Then on the basis of an erroneous report, the tenders carried out anti-submarine operations in the Celebes Sea from the 15th to the 19th.

21 January:
MIZUHO and CHITOSE departed Bangka for Kendari occupation duty. Provided direct escort for the Kendari invasion group against air and submarine attack and patrolled ahead of the route.

24 January 1942:
Arrived in the morning at Sarabanka Bay [Salabangka] and remained there conducting suppport operations for the Sasebo Special Landing Force's occupation of Kendari, Celebes.

26 January:
Flagship CHITOSE and Desdiv 16 departed for Bangka anchorage, separating from MIZUHO which remained behind.

29 January:
Because the Kendari operation was going smoothly ahead of schedule, MIZUH0 was released and assigned to the Ambon invasion operation. However, she does not proceed to Bangka to join CHITOSE, but left direct for Ceram Island [adjacent to Ambon] that same day.
0940 MIZUHO departed Salabangka anchorage with Patrol Boats 34 and 39 and six fishing boats. In addition her aircraft provided cover for Desdiv 16, 21st Minesweeper Division, and and 1st Subchaser Division elements of the invasion force that had already departed ahead of MIZUHO two hours earlier.

30 January:
1000 Rendezvoused with CHITOSE south of South Mangoli Island. The tenders operate in the strait, performing covering operations and harrassing recon-raids against Namlea.
Evening: Both tenders departed for Kelang Bay (west of Ceram)

31 January 1942:
0550 MIZUHO and CHITOSE arrived at Ceram, laying to in the Kelang anchorage on its southwest tip. Landings at Ambon commenced, but the weather is poor and air operations impossible.

1-2 February 1942:
Same assignment continued. 2nd Air Unit directed to patrol over the Ambon convoy and defend against air and submarine attack as it had for the Menado Convoy. Its aircraft carried out forceful attacks in support of the land forces with about 70 aircraft each day. Others patrolled the Banda Sea.

3 February:
1500: MIZUHO departed Kelang anchorage for Kendari with Patrol Boat No.39 and three guard ships to participate in the Makassar occupation. Once more Seaplatendiv 11 separated - CHITOSE stayed behind, departing for Piru Bay with Patrol Boat No.34 [just to the east on the Ceram coast] four hours later.

4 February:
1500: Arrived at Staring Bay.

6 February:
1930: Departed Staring Bay, bound for the Flores Sea to rejoin CHITOSE for the Makassar seizure operations.

7 February:
Arrived at Calowana Bay, then shifted to nearby Wajyo Bay. Departed that evening.

8 February:
0720: MIZUHO rejoined flagship CHITOSE southwest of Kabaena Island in the Flores Sea. Proceeded westward. That evening, in bad weather and poor visibility, the invasion forces began landing operations at Makassar around midnight continuing through the early morning.

10 February:
0340 While at anchor southwest of Bulunrue Island MIZUHO and CHITOSE are attacked by enemy aircraft in the Lassa Sea. No damage received by MIZUHO. However, CHITOSE is damaged.[2]
1920 CHITOSE departed for Jolo to support the Eastern Java invasion operations with Patrol Boats No.34 and No.38.

11 February:
1900: MIZUHO departed Makassar Strait for Kendari for necessary maintenance of her aircraft with Patrol Boat No.39 and SC No.2. Assigned to next cover the seizure of Bali Island's airfield.

12 February:
Returned to Staring Bay with Patrol Boat No.39.

16 February:
MIZUHO and Patrol Boat No.39 incorporated into the Second Escort Unit.

17 February:
1400: MIZUHO departed Kendari with Patrol Boat No.39 to support the Timor occupation operations.

18 February:
Morning: Arrived at east side of Binongko Island [southeast of Celebes in the western Banda Sea], and set up a seaplane base for the day. Departed again in the evening.

19 February:
0600: MIZUHO arrived off the northern coast of Lomblen Island [or Lonbulen] and set up a seaplane base in at Lewaring Bay; covering the advance of the 1st Echelon of the Kupang Invasion Force.

20 February:
Landings on Timor. MIZUHO departed above place and provided support for the ground action from the waters south of Alor Island.

21 February:
1000: Released to join orignally assigned unit (2nd Air Unit) and Eastern Java Invasion duty. MIZUHO departed in the evening for Makassar.

23 February:
Diverted to the the Gulf of Bone, Celebes, arrived there. Conducted maintenance work overnight.Patamalang Bay.

24 February:
1000: Though there has been hardly a break in operational tempo or time to service her aircraft, departed to hasten to rejoin CHITOSE and the southbound 1st Unit for the invasion of Java.

25 February:
South of Sebuku Island, Borneo, MIZUHO and Patrol Boat No.39 rendezvoused with CHITOSE and Patrol Boats No.34 and No.38. Seaplatendiv 11 is now nearly at full strength because CHITOSE is also serving the aircraft of the crippled SANUKI MARU, lying at Balikpapan.

26 February:
CHITOSE and MIZUHO anchored off Cape Selatan. Departed same day. Both tenders proceeded westwards toward Cape Puting while covering the Java invasion forces.

27 February:
Seaplatendiv 11 dropped anchor off Cape Puting. From there they conduct operations during the Battle of Java Sea that day. The weather is unfavorable from their location, and very few flights are made. Departed that evening southward with the convoy towards Bawean Island.

28 February:
MIZUHO and CHITOSE dropped anchor off the west coast of Bawean Island.[3] They release their Patrol Boats to join closer escort of the invasion convoy now headed in to Kragan. Their aircraft provided guards against the remaining ABDA ships and air attacks. However, the enemy remnants are not sighted. Three small gunboats and eight torpedo boats are sighted in Surabaya channel.

1 March 1942:
With CHITOSE is still anchored off the west side of Bawean Island. It had been discovered that the waters extending out from Kragan beach were shallow for a considerable distance, and not fit for a seaplane base. Therefore, Seaplatendiv 11 was to remain anchored off Bawean for the time being instead while surveys off the beaches on both sides of Cape Arawara and Seram beach were conducted.
Action:
- 0715 MIZUHO launched three F1M2 Type 0 "Pete" seaplanes.
- 0800 MIZUHO launched two F1M2 Type 0 "Pete" seaplanes.
- 0930 MIZUHO planes launched at 0800 returned. The two planes had expended 500 rounds of 7.7mm ammunition.
- 0945 Desron 4 staff's report of air attacks on the assembled transports caused RADM Fujita to curtail further ground support, and have his aircraft directly guard the convoy forces from overhead. During the day the unit's Jakes claim three Northrop light bombers shot down.
- 1015 All MIZUHO planes returned.{Those launched at 0715} "(No enemy sighted.)"
- 1103 Comcrudiv 5 reported enemy cruiser and destroyer sighted west of Bawean Island.
- 1140 From CO Seaplattendiv 11 to CO Crudiv 5, CinC Third Fleet: "For the purpose of attacking the enemy cruiser, launched two observation planes, 1140." [probably `we' is Seaplatendiv 11 flagship CHITOSE, but could be MIZUHO. This is noted because at a time unspecified MIZUHO launched two F1M2s armed with four 60 kg bombs. The message may well be referring to them.]
- 1240 Eleven F1M2 Type-0 observation planes take off for a bombing attack on an enemy cruiser and destroyer reported sighted west of Bawean Island by Crudiv 5 at 1103. However, they are unable to find either the enemy or Japanese units chasing them due to tropical squalls. Not until well after the two ships [HMS EXETER and HMS ENCOUNTER]have been sunk do they spot friendly units.[4]
- c1430 The flight sights one enemy destroyer ahead of the friendly units and bombs it.[The destroyer is USS POPE and cruiser seaplanes of Main Force [ASHIGARA, MYOKO] and Crudiv 5 [NACHI, HAGURO] are also present. One of them scored a near-miss off POPE's port side aft of amidships. This inflicts mortal flooding of the port engine room that within half an hour slows the ship to a crawl. POPE is then finished off by more near-misses from six Type-97 "Kates" from RYUJO and 8-inch gunfire from the cruisers ASHIGARA and MYOKO, sinking shortly before 1540.]

2 March:
Seaplatendiv 11 sets up a base at Karangdawa three nautical miles west of Cape Awarawara. Continued to provide cover and patrols for the invasion forces.

3 March:
Departed Bawean Island west coast with CHITOSE and Patrol Boats No.34,No.38 and No.39 for Kendari.

6 March:
Arrived at Kendari. Carried out repairs to engines and the hull along with basic maintenance.

9 March:
Departed Staring Bay with CHITOSE and Patrol Boats No.34, No.38, and No.39 back for the the Cape Awarawara zone. However, that same day, the Dutch commands in the East Indies surrendered.

12 March:
MIZUHO and CHITOSE arrived at Kragan. The invasion achieved, the seaplane base was dismantled.
2000: CHITOSE, MIZUHO, and departed Kragan for Makassar, the operation completed.

14 March 1942:
1130: Arrived at Makassar. Assigned to Southern Force Main Unit (still in Seaplatendiv 11, attached to Combined Fleet). Proceeded to Yokosuka via Staring Bay, Makassar, and Davao.

16 March:
MIZUHO departed Makassar for Yokosuka via Davao.

19 March:
MIZUHO arrived at Davao.

22 March:
MIZUHO resumed voyage to Yokosuka; departed Davao.

28 March 1942:
Arrive Yokosuka. Enters drydock for refitting the following day.

2 April 1942:
Undocked.

9 April 1942:
Assigned with Seaplatendiv 11 to Forward Force.

10 April:
Combined Fleet orders Stage Two - first phase put into action: The operations for the invasions of Port Moresby and Tulagi is to commence in late April thru mid-May. MIZUHO assigned with Cardiv 5 [SHOKAKU, ZUIKAKU] and SHOHO to the Fourth Fleet.

18 April:
Action:
MIZUHO attacked in dock at Yokosuka during the "Doolittle Raid." No damage is received, but the adjacent RYUHO (former TAIGEI) being recast as an aircraft carrier is damaged. The B-25 pilots saw the tender and RYUHO and reported them as two carriers under construction.

1 May 1942:
Noon: MIZUHO departed Yokosuka for Hashirajima upon completion of refitting.[5]
Action:
- 2315 the same evening, hit in port side aft of amidships by one torpedo of two fired by USS DRUM (SS-228; sub gives 2303 as the time) in a position bearing 220 degrees, forty miles from Omae Zaki. The torpedo struck between the port engine room and generator room and both flood. A fire broke out below decks and the tender assumed a list of 23 degrees. The tender is still able to move on her starboard engine and shaft, but to little avail.
- 2319 MIZUHO radios that she has been torpedoed in position 34-46'N, 138-14'E.
- 2329 List to port 29 degrees.
- 2334 MIZUHO's transmitting power faded in mid-transmission. Fortunately, rescuers had heard the initial messages and were already en-route.

2 May 1942:
- 0030 TAKAO and MAYA of Crudiv 4 arrived to assist. They had departed Yokosuka for Hashirajima four hours after MIZUHO did and raced to the scene.
- 0100 MIZUHO's condition was critical but somewhat stabilized. The tender was unnavigable, but the list was holding at 25 degrees to port. Towing by the cruisers had proved impossible. There was concern the fire was going to explode the bomb storage or the fuel and av-gas tanks. All radio equipment was unuseable. But flooding boundaries were established and pumping began while efforts were made to lighten the ship to reduce the list. All redundant equipment, furniture, and even the anchor's were dumped into the sea. But the fire continued to rage and its heat could be felt through the main deck.
- c0200 Despite strenous efforts to confine the flooding which appeared successful, the flooding now worsened three hours after being hit. Captain Okuma gave the order to Abandon Ship at 0330. The severely wounded were lowered into boats.
- 0400 List to port reached 39 degrees and the Captain ordered everyone left to leave the ship. Water had started to pour into open hatches at both ends of the ship. [6]

Sunk:
- 0416 MIZUHO capsized to port and began to go down by the stern. There came a large internal explosion, then the bow rose vertically and she sank. Heavy cruisers TAKAO and MAYA had arrived and rescued ComSeaplantendiv 11, ComAiron 23, ComAirRon 23, Captain Okuma, XO Cdr Nito, Gunnery Officer LtCdr Suzuki, Navigator LtCdr Kitajima, Chief Engineer Cdr (Eng.) Motohashi, Maintenance Officer Lt (Eng.) Suzuki, Damage Control Officer Lt (Eng.) Azuma), Surgeon Lt Konaka, Paymaster Lt Nagami, Communications Officer Lt Nagai, Air Officer Cdr Iwao, and 462 officers and men, but 7 officers and 94 men were lost. Among the survivors 17 were severely wounded, and 14 slightly wounded.

Captain Okuma is later appointed to the Staff of 1st Southern Expeditionary Fleet. Cdr Nito is later appointed XO of KASHII. LtCdr Suzuki is later appointed Gunnery Officer of HOSHO. LtCdr Kitajima is later KIA as Navigator of KINUGASA. Cdr (Eng.) Motohashi is later KIA as Chief Engineer of MIKUMA during the Battle of Midway. Lt (Eng.) Suzuki is later appointed Chief Engineer of CHOGEI, postwar. Lt (Eng.) Azuma is later KIA as Chief Engineer of YAHAGI. Lt Konaka is later appointed Surgeon of NOSHIRO and survives her sinking as well. Lt Nagai is later appointed Communications Officer of ATAGO. Cdr Iwao is later killed on Tinian as CO of Air Group 121.

20 May 1942:
Removed from Navy List.

Note 1 - These B-17s were of the 19th Bombardment Group. They had taken off from Malang, and staged from Samarinda, East Borneo before proceeding to Davao. Each carried four 600- pound bombs. No losses were sustained.

Note 2 - These aircraft were three USAAF LB-30s ("Liberator II" ) of the 19th Bomb Group (H) based at Malang, Java. They damaged Chitose.

Note 3 - Dutch reports gave the two seaplane tenders anchored position off Bawean Island as 05-45'S, 112-30'E.

Note 4 - The operations of Seaplatendiv 11 on 1 March 1942 are somewhat obscure. This is apparently due to the fact that they were wearing "multiple hats" and ComSeaplatendiv 11 had ordered them to limit operations to covering the convoy and sea interdictions. The attempt to attack the Exeter group was an exception, but still consistent with this priority. Seaplanes from the Main Force and Crudiv 5 seemed to have bombed USS Pope as well, so credit for the mortal near-miss is disputed. Though the participation of all three seaplane elements has been confirmed, to date it remains very hard to determine which group got the killing near-miss. The last direct hit scored was by 8-inch shell forward just as Pope was sinking at 1535-1540. As a final note, it is worth mentioning that Pope's Captain Blinn claimed after his ship sank, Japanese planes went on to bomb Ashigara and Myoko in error! This just might explain the odd brevity about Seaplatendiv 11's activity in this sea action.

Note 5 - The nature and extent of this re-fitting has not been discovered. However, in addition to badly needed maintenance and upkeep it probably included elements to prepare Mizuho for her projected role in the Coral Sea operation.

Note 6 - The IJN technical department after study of the event concluded that the centerline bulkhead in the engine room made it too difficult to correct the list. This conclusion was further re-inforced by the capsizing of crusier Kako after submarine attack following Savo Island. This would not be the only time this concern emerged, but in retrospect the evidence is arguably still inconclusive whether such bulkheads were disadvantageous most of the time. Nonetheless, in Mizuho's case there can be little doubt that progressive flooding, and not the fire, caused the loss of the vessel.

Acknowledgements: Special thanks to Bill Somerville and Matthew Jones for contributing to this TROM.