False Dmitry III
False Dmitry III (Russian: Лжедмитрий III, tr. Lzhedmitrii III; died July 1612), historically known as Pseudo-Demetrius III, was the last and most enigmatic of three pretenders to the Russian throne who claimed to be the youngest son of Ivan the Terrible; Tsarevich Dmitry.
Supposed to have been a deacon called Sidorka, he appeared suddenly, from behind the river Narva, in the Ingrian town of Ivangorod, proclaiming himself the Tsarevich Dmitry Ivanovich, on March 28, 1611. The Cossacks, ravaging the environs of Moscow, acknowledged him as Tsar on March 2, 1612, and under threat of vengeance in case of non-compliance, the gentry of Pskov also "kissed the cross" (i.e., swore allegiance) to the thief of Pskov, as he was usually nicknamed. On May 18, 1612 he fled from Pskov, was seized and delivered up to the authorities at Moscow, and was secretly executed there.