By Ray Furlong
BBC News, Berlin
A ceremony has been held in Berlin to present more than 300 police officers from 13 European countries who will be working in Germany for the World Cup.
The foreign police are part of an unprecedented security operation
They are being deployed as part of efforts to combat football hooliganism.
For the first time, foreign officers in uniform will patrol jointly with their German colleagues.
Some will be deployed in plain clothes on the border to halt troublemakers and prevent them entering Germany, while others will work in uniform in cities.
The German police band provided a warm welcome to the 323 policemen and women from across Europe, at the start of a truly unprecedented security operation.
The aim is to prevent football hooligans disrupting the tournament, but also to stop misunderstandings between foreign fans and local police.
Bob Kenrick, from the British Transport Police, explained.
"I think the organisation for this tournament is excellent, and the whole idea of bringing us over is to make sure that there's a visibility of 'home policing' if you like, and the communication between us, the federal German police and the fans should stop any problems occurring that have happened in the past."
Britain has the largest contingent, with 82 officers, who will be in uniform and have powers of arrest.
There will also be plain clothes 'spotters' to pick out known hooligans in crowds.
Poland also has a large force amid fears in Germany that Polish hooligans pose the biggest threat.
Rafal Wasiak is spokesman for the Polish delegation and told the BBC: "We will have mixed patrols, and our police officers will in fact have the same authority and responsibility as the Germans."
The German Interior Minister, Wolfgang Schaueble, said this level of co-operation would have been unthinkable in the past.
It was, he added, a symbol of how Europe was growing ever closer together.