re: How Should Israel Apply the Law of Armed Conflict During the Siege of Gaza?

I'll re-post my hypothetical from earlier for discussion:

President Biden and his Democrat administration order a secret attack on Russia. Russia responds by seiging America with a barrage of indiscriminate rockets and missiles in preparation for a full-scale ground invasion. The Biden administration orders a stop on all Americans attempting to flee the U.S. and avoid the war. There is no way out and all civilians and their families are forced to remain in the conflict zone.

Although Russia has an obligation to mitigate civilian casualties, they use the same rationale you proposed. Does that change the calculation?