Answer:
1: They defeated the French and indians in Fort Duquesne,
1: The Indians want to join England in battle for protection from them,
1:They now control said Fort Duquesne
2: Mr. Forbes is telling the Prime Minister that they defeated the french in the Fort Duquesne and the indians fled the french to join the English in battle, in return they seeked protection from the English, in defeating the French they won back the burned Fort Duquesne.
3: This would allow Prime Minister William Pitt to know what is happining in Fort Duquesne, allowing him to determine if he needs to send troops, supplies, transportation, or other means of war supplies.
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