Commitment Problems Drive Preventive War
The commitment problem—best understood through preventive war—occurs when an opponent will be much stronger in the future and you could head that off now by attacking; even though the rising power could promise a good deal later or give up something now, when they cannot credibly commit to honor that promise (because there's no enforcement architecture), the bargain breaks down and war becomes attractive, as seen in WWI (Russia's rise vis-a-vis Germany), the Iraq invasion (Saddam's potential WMD), and Russia's fear of a Western-armed Ukraine.