An alliance can be a nuclear warning sign
In Civilization VI, an alliance is more than a promise to cooperate: it creates a formal diplomatic relationship with shared benefits, such as better information or bonuses tied to the alliance type. While it lasts, the partners cannot simply treat each other as ordinary targets. A player who wants to attack an ally must first break that relationship and declare war.
That makes an alliance especially consequential once nuclear weapons enter the game. A nuclear strike can devastate a city and the surrounding area, but launching one against an ally means crossing a diplomatic line before the weapon even flies. The alliance is therefore both protection and a visible commitment: breaking it announces hostile intent.
Deterrence, not guaranteed mutual destruction
The danger is that a nuclear attack may invite retaliation. If both empires have nuclear weapons and can reach each other, striking first could leave the attacker facing a counterstrike. Each player must weigh the immediate damage against the possibility of losing cities, units, and territory in return. The alliance can buy time and make an attack harder to initiate, but it cannot make either empire invulnerable.
That is the logic behind the joke about one misclick turning both empires into radioactive glass. The game does not guarantee a perfectly balanced exchange; the outcome depends on each player’s weapons, defenses, and choices. But when two nuclear powers share a border, cooperation may be less about trusting the other player than about making sure neither has a safe reason to start the war.
