The Unknown War is a military history book written by Hienadz Sahanovich. It describes the events of the war between Tsardom of Russia and the Polish–Lithuanian Commonwealth in 1654-67. The war has become known as a part of the "Deluge", a series of military conflicts that overwhelmed the Polish–Lithuanian Commonwealth in the middle of the 17th century which included the Khmelnytsky Uprising, the Swedish invasion, and the Russian invasion among others.