The military force prepared to fight an extraterrestrial civilization was ultimately directed at humans. The extraterrestrial civilization participated in the Fourth War through its absence. Both sides in the war were human. After the Declaration of Extraterrestrial Intervention, the stellar alliances shared the same observational data. The Central Union government adopted neither side’s interpretation as official common-defense policy. The interpretations diverged. The hawkish stellar alliances argued that because external intelligent intervention could not be ruled out, surveillance networks and reserve power facilities had to be expanded. The pro-reduction stellar alliances opposed them, arguing that increasing the flow of energy before the cause had been identified would increase the deficit as well. The hawkish alliances installed detectors and blocking devices at passage entrances. The pro-reduction alliances demanded disclosure of the energy required to manufacture and operate those devices. Neither side could explain the cause of the deficit. Each accused the other’s policy of reducing the galaxy’s chances of survival. Early in the war, both alliances were cautious about attacking the other side’s facilities. Instead, they restricted access to observational data and suspended supply contracts for power-generation equipment. The hawkish alliances stockpiled reserve power in the galactic outskirts, while the pro-reduction alliances lowered the priority of military cargo on passages under their control. The effects reached stellar alliances belonging to neither side. The two camps were divided not by the locations of planets but by the routes to which they were connected. Entrances belonging to opposing camps could exist within the same star system, and the effective habitation zone shifted according to which side received power. Because closing passages completely would violate the right to connection, both sides adjusted opening times, safety inspections, and transport order in ways favorable to their own camp.
Armed clashes occurred sporadically at some management facilities, but the number of combat deaths was not high. Neither side wanted the conflict to escalate. The main reason later historical commissions classified this period as the Fourth War, with the subtitle Cold War, was that both sides exercised wartime mobilization powers and controlled stellar output so that it would not be supplied to the opposing camp. Since neither side formally declared war, there was no formal peace agreement either.
During the Cold War, the two sides conducted deficit research separately. Duplicate sets of equipment were installed to verify the same data, and each side demanded additional tests because it did not trust the other’s analysis. The expense was the cost of distrust, but it also helped uncover some defects. For that reason, the duplicated research could not be classified simply as waste. As time passed, both alliances acknowledged the problem of maintenance cost. The surveillance networks of the hawkish stellar alliances continued to grow without detecting an attack, while the pro-reduction stellar alliances failed to present a way to reduce facilities while also preserving the rights of existing citizens. The two camps agreed to begin with a joint investigation of passages that had no users. The joint investigation produced the agreement necessary for the first passage-closure plan. That agreement informally took the place of a peace treaty.