https://www.youtube.com/watch?v=takl4fei1pQ
TL;DR — The world has transitioned from a unipolar moment dominated by the US to a dangerous multipolar world with great powers like the US, China, and Russia, making great power war a relevant concern again. From a realist perspective, war is an inherent and dominating feature of international politics, driven by fundamental disagreements and the anarchic nature of the international system, and it tends to escalate beyond political control, especially in the nuclear age.
Takeaway — War is an endemic and unavoidable aspect of international politics, driven by fundamental disagreements and the structure of the international system, and its potential for escalation and destructiveness demands constant attention, especially from policymakers.