The Second Part of Khaibar conquered

When the Prophet [pbuh], along with his army, moved to this part of Khaibar, Al-Katiba, he laid a heavy siege to it for fourteen days with the Jews barricading themselves inside their forts. When he was about to use the rams, the Jews realized that they would perish, therefore, they asked for a negotiable peace treaty.

There is one controversial point in this context. Was this part of Khaibar (with its three forts) conquered by force? Ibn Ishaq clearly stated that Al-Qamus fort was conquered by force. Al-Waqidi, on the other hand, maintained that the three forts were taken through peace negotiations, and force, if any, was resorted to only to hand the fort over to the Muslims; the two other forts surrendered without fighting.