<P> Early on 3 May, Shima's force arrived off Tulagi and began disembarking the naval troops to occupy the island . Tulagi was undefended: the small garrison of Australian commandos and a Royal Australian Air Force reconnaissance unit evacuated just before Shima's arrival . The Japanese forces immediately began construction of a seaplane and communications base . Aircraft from Shōhō covered the landings until early afternoon, when Gotō's force turned towards Bougainville to refuel in preparation to support the landings at Port Moresby . </P> <P> At 17: 00 on 3 May, Fletcher was notified that the Japanese Tulagi invasion force had been sighted the day before, approaching the southern Solomons . Unknown to Fletcher, TF 11 completed refueling that morning ahead of schedule and was only 60 nmi (69 mi; 110 km) east of TF 17, but was unable to communicate its status because of Fletcher's orders to maintain radio silence . TF 17 changed course and proceeded at 27 kn (31 mph; 50 km / h) towards Guadalcanal to launch airstrikes against the Japanese forces at Tulagi the next morning . </P> <P> On 4 May, from a position 100 nmi (120 mi; 190 km) south of Guadalcanal (11 ° 10 ′ S 158 ° 49 ′ E ﻿ / ﻿ 11.167 ° S 158.817 ° E ﻿ / - 11.167; 158.817), a total of 60 aircraft from TF 17 launched three consecutive strikes against Shima's forces off Tulagi . Yorktown's aircraft surprised Shima's ships and sank the destroyer Kikuzuki (09 ° 07 ′ S 160 ° 12 ′ E ﻿ / ﻿ 9.117 ° S 160.200 ° E ﻿ / - 9.117; 160.200) and three of the minesweepers, damaged four other ships, and destroyed four seaplanes which were supporting the landings . The U.S. lost one torpedo bomber and two fighters in the strikes, but all of the aircrew were eventually rescued . After recovering its aircraft late in the evening of 4 May, TF 17 retired towards the south . In spite of the damage suffered in the carrier strikes, the Japanese continued construction of the seaplane base and began flying reconnaissance missions from Tulagi by 6 May . </P> <P> Takagi's Carrier Striking Force was refueling 350 nmi (400 mi; 650 km) north of Tulagi when it received word of Fletcher's strike on 4 May . Takagi terminated refueling, headed southeast, and sent scout planes to search east of the Solomons, believing that the U.S. carriers were in that area . Since no Allied ships were in that area, the search planes found nothing . </P>

Who started the battle of the coral sea