Che Guerrero is a province owner of the Postmodern Era and owner of the provinces: Cai Chet Nui and Rung Chien Dau. Both provinces are available at the start of the Postmodern Continent Map, and he is the first province owner to have two wave defending armies, though his armies consist of less numbers of units in each wave and units one or two eras behind.
As soon as you scout his provinces, a side quest comes along by General Grivus telling you to avoid combat and negotiate with him. If you did negotiate with him, he would be cheerful and would do good business with you, also giving you MG Teams. If you fought him, he would constantly attack you and you would have to defend yourself as requested in the Story.
Once you get both his provinces, he would be checkmated and have no more influence anymore. After you do business with him, it doesn't matter whether you get his other province peacefully or forcefully.
Real Life Basis
He is based on the real-life character Che Guevara, who was Argentinian Marxist revolutionist as well as a Guerilla Leader. He is well known for his efforts in the Cuban Revolution.