The monastery baptized Ivan the Terrible, the notorious Russian tsar. He fortified it into a solid fortress to defend Moscow. In the 1550s a thick wall with brick-and-stone towers substituted the wooden fence.
In 1606 the well-famed though short-termed Russian Tsar Boris Godunov with his family were buried by the Dormition Cathedral.
In 1608-10 the Trinity Monastery survived a siege by 30K Polish invaders for 16 months. This feat of arms spread the word about its defenders and won it immense prestige.
Peter the Great kept maintaing its status as a royal fortress. In 1689 he hid inside the monastery during the streltsy (royal guard) riot in Moscow.