What does Senator Gravel mean when he says, “. . . the enemy knew what we were not permitted to know” in the pentagon papers?

Montezuma was taken prisoner by the spanish and held captive for months while the spanish ransacked the city of tenochtitlan. what was the fate of montezuma? a he escaped only to be cut down in battle.b he reasoned with the spanish and got them to leave the city.c he died of old age while in the custody of cortes.d he was struck with stones trying to plead for peace with his people and it is reported he died a few days later.