Unexpectedly, each party having an ultima ratio turned the tables.

Unexpectedly, each party having an ultima ratio turned the tables. Both sides were afraid to use it. But the fear of the enemy using the 'nuclear club' was even stronger. That lead to the cooldown of military operations; several decades later, a reluctant peace was made. Though not at once, both countries managed the economical conversion. But the search for external enemies never seized completely...