Multipolar (4+) power balances tend to be the least stable (see: WWI & WWII), due to temporarily alliances believing they possess superior force and making a fi

Multipolar (4+) power balances tend to be the least stable (see: WWI & WWII), due to temporarily alliances believing they possess superior force and making a first strike. Afaik, tripolar tends to be the most stable, with a default-neutral third party, who may choose to side with either other major. Bipolar comes in second.