Abe 's ships departed Rabaul for the 840 nmi ( 970 mi ; 1,560 km ) trip to Port Moresby on 4 May .
Abe 's ships were joined by Kajioka 's force the next day .
Abe 's ships departed Rabaul for the 840 nmi ( 970 mi ; 1,560 km ) trip to Port Moresby on 4 May and were joined by Kajioka 's force the next day .