Proportionality in armed conflict.

As we await Israel's response to the Iranian attack over the weekend, the question of 'proportionality' comes to the fore.

Given the readiness and effectiveness of Israel's rocket defences, it is not surprising that few of the rockets (cruise and ballistic) actually landed and there was only one injury. While Israel did the heavy lifting in the defence, various allies helped out including Jordan. This raises the question of whether the response should be proportionate to Iran's intention (catastrophic) or proportionate to the results of the attack (minuscule).

The general military consensus seems to be that the response should be proportionate to the intention and this hypothetical illustrates the way the reasoning works.

Two countries A and B are at loggerheads. After years of belligerent rhetoric, A finally snaps and launches a nuclear ballistic missile against B. Soon after launch, B detects A's missile and launches its own. While both missiles are in the air, A's missile malfunctions and falls harmlessly into the sea. B's missile however continues its planned flight and destroys a major city in country A.

Should B's enemies scream from the rooftops that its response causing massive damage was disproportionate?

The totality of Iran's rockets was estimated at 60 tons of explosive.