Complex sentence: Pitt significantly increased British military resources in the colonies, while France was unwilling to risk large convoys to aid the limited forces it had in New France, preferring instead to concentrate its forces against Prussia and its allies in the European theatre of the war.
Split into simpler sentences: Pitt significantly increased British military resources in the colonies at a time when France was unwilling to risk large convoys to aid the limited forces it had in New France. It concentrated its forces against Prussia and its allies in the European theatre of the war.