President Obama called for a new "fighting spirit" of citizen activism in the free world, as he renewed calls to reduce US and Russian nuclear stockpiles in a speech at Berlin's Brandenburg Gate.
In a wide-ranging address that comes nearly 50 years after John F. Kennedy's famous Cold War speech he said:
"Today's threats are not as stark as they were half a century ago, but the struggle for freedom and security and human dignity, that struggle goes on.
"And I come here to this city of hope because the test of our time demands the same fighting spirit that defined Berlin a half-century ago."
More top news
After a sweltering day, where temperatures reached a record high for July, the weather turned.
One of Britain's leading tour operators, Thomas Cook, has joined a growing push for changes to the way tourists receive security warnings.
Thunderstorms affect mostly southeast England on Thursday with a mixture of sunny spells and showers into the afternoon.