Advice on two points

You have to read the fine print of the insurance policy. Each company is different--most limit the reasons you can cancel, including war. Even "cancel for any reason" policies won't cover you 100%. Many insurance companies require you to purchase it after the first payment on the trip is made while others allow you to purchase up until 48 hours before your departure. So, like everything else, the answer is "it depends".

https://www.roamright.com/travel-insurance-blog/how-travel-insurance-works-during-geopolitical-instability/#:~:text=In%20general%2C%20travel%20insurance%20benefits,and%20dismemberment%20benefits%2C%20and%20others.

How Travel Insurance Works During Geopolitical Instability
By Victoria Zidwick Published on Tuesday, January 14, 2020
Exclusions to Know

In general, travel insurance benefits are not payable for any loss due
to war, invasion, acts of foreign enemies, hostilities between nations
(whether declared or undeclared), or civil war. This would include
emergency medical benefits, trip delay benefits, accidental death and
dismemberment benefits, and others.

In addition, political and security evacuations are not covered when
the evacuation is from the traveler’s home country, when the event
occurs prior to the traveler’s arrival in the country, or when seven
days have passed between the event and the traveler’s request to for
assistance. There are other exclusions that may also apply. These can
be found in your policy documents.

If you are planning a trip to a volatile area of the world, make sure
you understand your coverage limits and exclusions. If you have
questions, please call our customer service team and they can help
explain any details that may be most relevant to your situation.

Note: Available plans and coverages may have changed since this blog
was published.