Kazantsev commanded the United Group of Forces in the North Caucasus in 1999-2000. He led operations against militants in Chechnya and Dagestan. In May 2000, Kazantsev was transferred to the reserve. After that he was appointed Presidential Plenipotentiary Envoy to the Southern Federal District. He worked in this position until March 2004. The general was a member of the operational headquarters for the management of counterterrorism actions in the North Caucasus region.
The title Hero of Russia was awarded to Kazantsev in December 1999 for the anti-terrorist operation in Dagestan and Chechnya. He was also awarded the Order for Military Merit, the Order of Friendship, and the Medal for Military Merit.