He ordered the mass killing of 20,000 Ottomans

In addition to defeating the Saxons, Tepes faced threats from the Ottoman Empire, his former captives, and friends.

Mehmed retaliated by attempting to ambush Tepes as he traveled to Giurgiu, an Ottoman stronghold. Tepes discovered the scheme and apprehended the conspirators, who he later impaled at Targoviste. Then, after masquerading as an Ottoman and ordering the gates to be opened in fluent Turkish, his soldiers assaulted the building and massacred the garrison, capturing Giurgiu. Tepes began an audacious and successful campaign of guerilla warfare in the winter of 1461–62. He divided his army into small groups and attacked the Ottoman strongholds with a combination of absolute bravery, speed, and brutal ruthlessness.

Finally, Mehmed launched an invasion of Wallachia with 60,000 troops and an arsenal of cutting-edge weapons. Tepes changed his strategy to one of scorched earth, strategic retreat, and increased guerilla attacks because his army only had 24, 000 soldiers. In 1462, Tepes led the infamous Night Attack at Targoviste while the Ottomans were camped outside of the city, killing some 5,000 adversaries. The infamous "forest of the impaled," a mile-long semicircle of 20, 000 impaled Ottoman prisoners rotting in the sun, met the Ottomans as they prepared to start their attack on Targoviste. Mehmed gave the command to withdraw his troops the following day.