Nevertheless , Fletcher decided the risk was necessary to ensure the Japanese invasion forces could not slip through to Port Moresby while he engaged the carriers .
Detaching Crace reduced the anti-aircraft defenses for Fletcher 's carriers .
Fletcher decided the risk was necessary to ensure the Japanese invasion forces could not slip through to Port Moresby while Fletcher engaged the carriers .
Detaching Crace reduced the anti-aircraft defenses for Fletcher 's carriers .