What happened to occur before allied forces concentrate solely on the pacific front

The surrender of Germany made the allies focus only on the pacific.

Explanation:

There were two main fronts of the war.

One was the European land where the Germans were fighting the allies and also Italy that had had an early surrender.

The pacific front was controlled by Japan and its expansionist lands.

When Italy surrendered Europe was completely on Germany and when eventually Germany fell the war remained in pacific.

The war in pacific was thus the only thing that the allies had to focus on by the end of the war.