TIMBUKTU, MALI—German diplomats provided invaluable assistance with the rescue of more than 200,000 historic books and manuscripts from Timbuktu’s libraries before they could be destroyed by Islamist rebels. The most important documents were smuggled to safety in secure storage boxes, hidden with shipments of lettuce and fruit. “Now we need to preserve them for posterity,” said Guido Westerwelle, Germany’s Foreign Minister.