Israel hit a Houthi leadership conference and succeeded in killing a dozen or more of the Houthis’ top leaders, including their “prime minister” and “foreign minister” while injuring several other attendees. In the Wall Street Journal article describing the attack and its implications, the news writers noted that

Until Thursday’s strike, Israeli retaliation for Houthi attacks had largely been limited to infrastructure like ports and power stations.

Then they quoted Oded Ailam, ex-Mossad official and currently of the Jerusalem Center for Security and Foreign Affairs:

Israel has abandoned the old formulas of proportional retaliation[.]

As it should. The old formulas had nothing to do with proportionality, for all that their users insisted so. Those old formulas centered on tit-for-tat responses, which did nothing to deter future attacks, but did succeed, very effectively, at running up casualties, especially civilian, on both sides as a result of repeated and escalating tit-for-tat exchanges of retaliations.

There’s nothing at all proportional in a strategy that increases casualty rates rather than reduces them.

True proportionality is much more than retaliating in the moment after an in-the-moment attack. Proportionality done correctly, which includes serious consideration of the morality of the response, takes a longer view and considers how a current retaliation would impact future attacks by an enemy and so impact the civilian casualties associated with those future attacks as aggregated to the damage done—civilian as well as military—by a proximate retaliation. A truly proportional retaliation would mitigate, if not preempt, those future attacks by being sufficiently heavy and not immorally tit-for-tat.