The Israel Defense Force says that it stopped an attempted cyber attack launched by Hamas over the weekend, and retaliated with an airstrike against the building where it says the attack originated from in Gaza. It’s believed to be the first time that a military has retaliated with physical violence in real time against a cyberattack.

Violence erupted this weekend as Hamas and the IDF launched attacks against one another in the last three days. Hamas fired more than 600 rockets into Israel, while the IDF conducted its own strikes against hundreds of what it characterized as military targets. Thus far, at least 27 Palestinians and four Israeli civilians have been killed, with more than a hundred wounded. Tensions between Israel and Hamas have grown in the last year, with protests and violence erupting periodically. Reuters and The Wall Street Journal have good overviews of the situation.

During the battle on Saturday, the IDF says that Hamas launched a cyberattack against Israel. It didn’t reveal what the target was, but told The Times of Israel that it was designed to “[harm] the quality of life of Israeli citizens.” It also indicated that the attack didn’t appear to be sophisticated and was quickly stopped. An IDF spokesperson told the publication that “Hamas no longer has cyber capabilities after our strike.”

The IDF released video that it says is of the building that the cyberattack was launched from.

Here is the video released by the IDF showing the air-strike against the building housing Hamas cyber forces. pic.twitter.com/uHm2ZYa4AP — Catalin Cimpanu (@campuscodi) May 5, 2019

What’s novel about this particular incident is that it appears to be the first time that a military has met a cyberattack with a real-world response during an ongoing battle. As ZDNet’s Catalin Cimpanu points out, the US targeted a member of ISIS back in 2015 after he released US service member records online, but that attack didn’t occur in real-time. “Israel’s response against Hamas marks the first time that a country has reacted with immediate military force to a cyber-attack in an active conflict,” Cimpanu writes.

The attack raises serious questions about the incident, and what it means for similar incidents. A general principle of warfare and international humanitarian laws hold that attacks must be proportional in response. (For example, a country wouldn’t be permitted to launch a nuclear missile against a capitol city if a single soldier is killed in a border skirmish.) Given that the IDF admitted that it had halted the attack prior to the airstrike, the question is now whether or not the response was appropriate. Either way, it opens up a worrying evolution in the state of modern warfare, given the threat that computer hackers can pose to military forces or nations.