The Navy’s 4th Signal Unit is formed under the Truk-based 4th Base Force.
Source: JACAR, 4th Base Force
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1941
All Kosraean males aged 12 to 60 are called to the Lelu playground for compulsory military training.
Source: Habele, Kosrae
The Navy’s 4th Base Force arrives at Truk and is reorganized there.
Source: JACAR, 4th Base Force
Takeshima airfield is enlarged for land-attack aircraft and a seaplane base is set up on Natsushima .
Source: ja.wikipedia チューク諸島
Japanese reportedly outnumber Pohnpeians around Kolonia and Palikir by a thin margin .
1942
The Navy’s 41st Guard Unit is formed at Truk.
Source: JACAR, 4th Base Force
The Navy’s 42nd Guard Unit is formed for Ponape, with a Kusaie detachment.
Last territory-wide count: 86,810 Japanese against 51,951 islanders.
Source: Miyauchi 2018
Kosrae’s radio station JPK is probably in full operation.
Source: Habele, Kosrae
1943
Truk, Ponape and Jaluit branches merge into the Eastern Branch at Truk; Ponape becomes a sub-office.
Palau and Yap branches merge into the Western Branch; Yap becomes its sub-office.
Source: JACAR, Yap branch
Chuuk is strongly garrisoned; about 38,000 outsiders and 10,000 Chuukese face growing hunger through 1945.
1944
Army troops that become the 52nd Independent Mixed Brigade land on Ponape; the brigade is formally reorganized in May 1944.
A US reconnaissance flight over Truk prompts Admiral Koga to pull the Combined Fleet back, mostly to Palau.
Source: NHHC, H-Gram 026-3
First US air raid on Ponape, by 40+ B-24s; Japanese Wikipedia dates the first large raid to 15 February.
US aircraft attack Kosrae; no ground battle follows.
Source: Pacific Wrecks, Kosrae
Operation Hailstone: 500+ US carrier aircraft strike Truk, destroying 250–275 of about 365 Japanese aircraft.
Source: NHHC, H-Gram 026-3
An Okinawan father is drafted locally; his evacuated wife and children survive a strafed, burning ship.
Source: Ryukyu Shimpo
Nimitz decides to bypass Truk.
Source: NHHC, H-Gram 026-3
Marine Corsairs fly the first fighter escort for B-25s over Ponape; a B-25G is lost.
Source: Pacific Wrecks, Ponape missions
US air missions against Yap, beginning 30 March 1944.
Source: Pacific Wrecks, Yap
A US raid wrecks the Asor weather station; the Japanese then remove 84 men and 15 women from Ulithi.
Source: Habele, Ulithi
The Army’s 51st Independent Mixed Brigade lands at Truk.
Source: JACAR, 51st IMB
US air missions against Woleai, starting 1 April 1944.
Source: Pacific Wrecks, Woleai
Task Group 58.2 strikes Truk again: airfields, Eten, the Dublon seaplane base and fuel tanks.
Source: VF-31 sortie history
About 7,000 Japanese soldiers arrive to defend Woleai and its airfield.
Source: Habele, Woleai
A US cruiser bombardment group shells Satawan in the Mortlocks and Ponape.
Japanese civilians in the Eastern Branch are evacuated to Japan, though about 5,600 Japanese remain on Ponape at war’s end.
The Army’s 49th Independent Mixed Brigade is formed to guard Yap’s naval airfield.
US forces occupy Ulithi without opposition, guided by men from Federai.
The US commander orders the people of Mogmog, Sorlen, Falalop and Asor moved onto Fassarai.
Source: Habele, Ulithi
A Japanese kaiten human torpedo sinks the US oiler Mississinewa in Ulithi lagoon, killing 63 crew.
Source: Wikipedia, USS Mississinewa
The Navy’s 43rd Guard Unit is reorganized with units based at Yap.
Source: JACAR, 4th Base Force
About 6,000 Japanese troops are based on Yap, two runways are built and about 3,000 islanders are moved inland .
Source: ja.wikipedia ヤップ島
3,811 army and 700 navy men under Lt. Gen. Harada dig tunnel bunkers into Kosrae’s peaks .
Source: Wikipedia, Kosrae
Navy crews build an airfield at Palikir, where the FSM national government complex now stands .
Source: Pohnpei-adventure
1945
Marine PBJ bombers strike Palikir Airfield No. 2, the last listed US mission against Ponape; one PBJ is lost.
Source: Pacific Wrecks, Ponape missions
The Navy’s 47th Guard Unit is formed at Truk.
Source: JACAR, 4th Base Force
British Pacific Fleet aircraft and cruisers attack Truk in Operation Inmate.
Source: Wikipedia, Operation Inmate
Truk’s commanders, including Lt. Gen. Mugikura Shunzaburō, surrender aboard USS Portland; navy units record a ceasefire.
US occupation and military government begin 2 September (JACAR); Col. Eto Daihachi surrenders aboard USS Tillman on 5 September.
Lt. Gen. Harada surrenders Kusaie aboard USS Hyman; Lt. P.F. Woodhouse stays as military governor.
Source: Last Stand on Zombie Island
The Ponape garrison signs the surrender.
Repatriation of Japanese from Yap begins; it is completed by March 1946.
Source: JACAR, Yap branch
The Hikawa Maru arrives at Kusaie on 4 November, takes on Japanese personnel and leaves 6 November.
Source: WW2DB, Kusaie
Repatriation of 14,173 army and 24,524 navy personnel from Truk to Uraga begins, running to 13 February 1946 .
Source: ja.wikipedia チューク諸島
Units of the 51st Independent Mixed Brigade leave Truk and Natsushima for Japan.
Source: JACAR, 51st IMB
Units of the 52nd Independent Mixed Brigade leave Ponape, landing at Uraga on 22 December 1945 and 5 January 1946.
Source: JACAR, 52nd IMB
About 5,600 Japanese live on Ponape per JACAR; Japanese Wikipedia says about 13,000 .
The central and eastern Carolines hold 14,066 Japanese, Okinawan and Korean civilians plus about 8,000 troops.
Gaps and conflicting sources
Notes from the research chronology for the years this era covers.
Japanese rule · World War II, 1914–1945
Years with no event found:
- None. Every year from 1914 to 1945 has at least one sourced row.
- Thin years: 1916 has only naval post-office records (weak); 1925 has only branch-head appointments; 1928 has only one weak school-founding row.
Notes on conflicts and gaps:
- Kosrae: none of the sources used here gives the October 1914 occupation date. It was never a separate branch office; it came under Ponape, then the Eastern Branch from 1943.
- Spanish Jesuit return: March 1921 (Jesuit Conference of Asia Pacific) or 1922 (MicSem).
- First Ponape raid: 14 February 1944 (Pacific Wrecks) or 15 February 1944 (Japanese Wikipedia). Pacific Wrecks lists missions to 6 February 1945; Japanese Wikipedia says major attacks ended in May 1944.
- Yap surrender: 2 September 1945 (JACAR, start of occupation) or 5 September 1945 (Pacific Wrecks, Eto aboard USS Tillman).
- Eastern Branch merger: 5 November 1943 (JACAR) or 4 November 1943 (one Japanese Wikipedia entry).
- 49th IMB on Yap: formed 9 July 1944 (JACAR) or reorganized May 1944 (English Wikipedia).
- 1926 school row: Japanese Wikipedia, as consulted for this site, dates the U and Ponape Japanese schools to 1926, while an earlier reading of the sources dated the Kusaie school to 1926. 『南洋群島教育史』 (1938) could settle this.
- Not found: 1925, 1930 and 1940 island-level census tables; any typhoon in 1914–45; shrine founding dates for the four island groups; a Japanese record of the Sokehs return. The Habele pages on State Shinto and the Puluwat lighthouse could not be opened, so they were not consulted for this site.