In season 4, he aids the humans in their plan to destroy the Espheni power core and manages to get his father to return to lend a hand. In season 5, Cochise continues aiding the 2nd Mass' war efforts and identifies the alien Tom saw as a Dornia, a believed-to-be extinct alien race that was the first conquered by the Espheni. Cochise's health begins failing due to a failing organ and he contacts his father to say goodbye. Anne Mason suggests an organ transplant from Cochise's father to save him, but his father initially refuses, feeling that Cochise has become too human. He eventually agrees and Cochise is saved, but his father dies. Cochise aids in the march on Washington, DC and is shocked to hear about the existence of the Espheni Queen. When Tom gets a biological weapon from the Dornia, Cochise aids Anne and Marty in modifying it so that its harmless to humans. Cochise helps explain the situation to another militia leader that arrives and is part of Tom's strike team to kill the Espheni Queen. He warns of the dangers of the Espheni hatchlings and is cut-off from Tom when they attack. Cochise witnesses Anne's death and the destruction of the Espheni by the Dornia bioweapon. Months later, Cochise is part of a Volm delegation who attends Tom's speech and the choosing of a new leader for a united humanity.