The app and sirens are a backstop to Israel’s extensive military defenses. The Iron Dome missile defense system effectively intercepts or destroys most airborne weapons headed to Israel. But some rockets have slipped through, causing injuries in recent days, and the government has encouraged people in Israel to download its app.

Across the border, Israel’s military has sometimes called people in Gaza to warn of its own attacks. But power and communications networks there have been unreliable since Israel’s recent assault began, and on Friday internet access appeared to be cut off entirely. The Home Front Command app doesn’t provide alerts for the disputed Hamas-controlled territory, as it is out of Israel’s jurisdiction, Zamir says.

Palestinian activists and tech entrepreneurs say no one appears to be trying to provide civilians of Gaza with an equivalent early warning system. Hamas did not respond to requests for comment.

If power and communications were intact, a warning app could technically operate in Gaza, perhaps in a similar way to a system that Western governments fund in Syria. Vetted users and social media scanning tools feed the app with observations about drones, missiles, and other military movement. Machine learning and other data analysis techniques determine which areas of Syria need warning. Alerts then ring through public sirens and messaging apps.

But it’s unclear who would be willing to stand up a system like that in Gaza, or how it could keep functioning as Israel’s assault continues. Communications networks have faltered over the past three weeks of Israeli air strikes, which have damaged key infrastructure. On Friday the last internet provider whose service was operating in Gaza, Paltel, and UK internet monitoring company NetBlocks reported that Gaza was wholly offline. Power generators are reaching their limits, according to the UN agency advocating for Palestinians, after Israel cut off electricity and fresh fuel.

“Tech solutions are invalid,” says Mohammad Alnobani, a Palestinian who is CEO of Arab-focused stock photography service Middle Frame, speaking ahead of Friday’s communications collapse in Gaza. He says trying to maintain contact with anyone inside Gaza right now is frustrating. “We usually lose touch with them and get back in touch every few days to make sure they are alive.”

App Surge

Israel’s smartphone early warning system has its roots in a 2012 side project started by a pair of Israeli software engineers. With sanctioned access to a government data feed, they developed an app now known as Red Alert : Israel to notify people when the street sirens—part of a system known as Red Color—that warn of incoming rockets go off. They aimed to reach people who may not have heard the sirens, perhaps because they were on the edge of town or driving.

Usage first became widespread during violence in 2014, when more than 1,400 Palestinian civilians and six Israeli civilians died, according to the UN. To encourage adoption, the developers designed an option to get alerts sent to the viral social app of the moment, Yo, which was otherwise known only for enabling users to exchange messages saying “Yo.” It later went out of business.

You May Also Like

Can AI Replace Humans? We Went to the Fast-Food Drive-Through to Find Out

What to Read Next This post first appeared on wsj.com

The 54 Best Prime Day Deals if You Work From Home (Day 2)

You may be going back to the office soon, but several companies…

The YOLOers vs. Distancers Feud Is Tearing Us Apart

Not only are the Distancers wrecking the school system and bludgeoning the…

Southern Appalachian Mountain streams are not the cleanest for drinking, study finds

Streams from the mountainous Southern Appalachian region provide clean drinking water to…