Complex sentence: They scrapped the idea because neither the British nor the Americans had informed the Soviets that they had captured key German archives, and sharing those papers with Stalin would have prompted the Soviets to inquire about the source of these records.
Split into simpler sentences: They scrapped the idea because neither the British nor the Americans had informed the Soviets that they had captured key German archives. Sharing those papers with Stalin would have prompted the Soviets to inquire about the source of these records.