Having learnt of Vlad's invasion, Mehmed II raised an army of more than 150,000 strong, that was said to be "second in size only to the one" that occupied Constantinople in 1453, according to Chalkokondyles. The size of the army suggests that the sultan wanted to occupy Wallachia, according to a number of historians (including Franz Babinger, Radu Florescu, and Nicolae Stoicescu). On the other hand, Mehmed had granted Wallachia to Vlad's brother, Radu, before the invasion of Wallachia, showing that the sultan's principal purpose was only the change of the ruler of Wallachia.