Truk was a fleet base until February 1944
Chuuk Lagoon served as the Combined Fleet’s forward anchorage until a US reconnaissance flight on 4 February 1944.11 NHHC, H-Gram 026-3 Admiral Koga then pulled the fleet back, mostly to Palau. Operation Hailstone struck on 17–18 February 1944 with over 500 US carrier aircraft.
The raid sank two light cruisers, four destroyers and 30 auxiliaries and merchant ships, plus smaller warships.22 NHHC Japanese tallies add a third light cruiser, Agano, sunk by a US submarine.33 ja.wikipedia
It destroyed 250–275 of about 365 Japanese aircraft, while the US lost 25 aircraft and 40 men.44 NHHC On 12 March 1944 Nimitz decided to bypass Truk.
Bypassed islands faced hunger, labor and bombing
About 38,700 Japanese army and navy personnel, later repatriated from Truk in 1945–46, shared Chuuk Lagoon with about 10,000 Chuukese until the surrender.55 Poyer, “Dimensions of Hunger,” via Habele; ja.wikipedia, Chuuk Most civilians had left by May 1944.66 JACAR, Truk
Chuukese memories center on food shortages. In the final months the military took breadfruit and other food from Micronesian farms.77 Wikipedia, citing Poyer et al.
US aircraft bombed Pohnpei from February 1944 to February 1945.88 Pacific Wrecks Japanese sources date the first raid to 15 February 1944, with heavy raids through May.99 ja.wikipedia, Pohnpei
Kolonia burned, crops were destroyed, and survivors sheltered in caves.1010 Pohnpei-adventure.com A 1944 airfield stood where the national government complex at Palikir now sits.
Yapese recall the war through bombing, labor drafts and “suffering,” and some war-claims disputes remain open.1111 Poyer, “Yapese Experiences,” via Habele Kosrae held about 4,500 Japanese troops under Lt. Gen. Yoshikazu Harada.1212 Wikipedia, Kosrae; Last Stand on Zombie Island No source yet covers Kosraean hunger or labor.
None of the four islands was invaded, so the war there meant siege rather than ground combat.
Surrender emptied the islands of settlers
Truk’s commanders surrendered aboard USS Portland on 2 September 1945.1313 NHHC photo archive, via ibiblio Lt. Gen. Mugikura Shunzaburō signed at Truk. Kosrae surrendered on 8 September aboard USS Hyman, and Pohnpei on 11 September.1414 ja.wikipedia, Chuuk; JACAR, Ponape; Zombie Island
Almost every Japanese settler was repatriated, and only 33 in the central and eastern Carolines stayed.1515 Wikipedia, citing Peattie and Poyer Children of mixed families stayed; a claim that 20% of citizens have Japanese ancestry is weakly sourced.