The German authorities will no doubt be hugely relieved: They finally successfully tested a nationwide warning system designed to be used in the case of any crisis. 

What is the early warning system?

It's a combination of sirens in public spaces and alerts sent to people's phones. 

When would it be used?

It could be used, for instance, if there's a terrorist attack, or a leak from a nuclear power plant, or a natural disaster such as a violent storm or heavy flooding. 

Why would the authorities be relieved?

The reason they'll be so relieved is that two years ago, when they first tested it, some of the sirens simply didn't go off and the warnings sent to people's phones took up to half an hour to arrive. 

Do other countries have a system like this?

Germany's certainly not the only country in Europe that has a similar system. In France, for instance, authorities test their sirens on the first Wednesday of every month in 2,000 villages and towns right around the country. It's a traditional check that has happened right since World War II. 

What the German government is saying is that they now have in place a system which will alert people if there is any danger – and could, in time, save lives.