Britain's wartime leader Winston Churchill famously called for a "United States of Europe" in a 1946 speech to the University of Zürich, inspiring future generations to create the economic alliance that led to the European Union.
After Churchill's dream of postwar integration came to fruition, initially with the creation of the European Economic Community in 1957, the United Kingdom became a pillar of the continent's growing economic and political alliance starting in 1973, and stayed on for almost a half-century.
But with the U.K.'s chaotic departure from the E.U. on Saturday, the continental organization and its leaders did some soul-searching while heading for uncharted territory, reduced to 27 member nations.
“This departure is a shock for Europeans. It is the first time a country has left the European community,” French President Emmanuel Macron said in a 'letter' to the British people.
"The U.K. was not there when it took its first steps in 1950, but we owe it so much — Winston Churchill’s historic foresight, for a start. And since 1973, while our European relationships may at times have been turbulent, the U.K. has been a central player in the European project — particularly in building the single market — a more influential player than the British have often themselves imagined."
Macron said the E.U. must acknowledge the lessons of Brexit, including how it is easy to cast blame on others, but also the need to be seen as more effective and more protective of Europe's citizens.
"I am convinced therefore that Europe needs new momentum, in a world where the need for control, security and protection is stronger than ever," he said. "I fight every day, and will continue to do so, for this united, sovereign and democratic Europe, whose strength will make our continent strong."
Strength in numbers
German Chancellor Angela Merkel called Britain's departure "a profound watershed moment" for all 27 nations that remain in the E.U., which would do everything possible to ensure the continent succeeds.
Though it is the first time any big nation has left the bloc — removing an important economic, military and diplomatic force — not much will change immediately, due to a transition period until the end of 2020.
"During this time, nothing will change for people who want to stay in or travel to the U.K. Likewise, nothing will change for companies producing goods and employing workers in the U.K. It remains to be seen what happens after this transition period," Merkel said in a statement.
"This means that we will now have to engage in most intensive negotiations with the British on our future relations in the area of trade and business. This will be the dominant issue this year," she said. "These negotiations will certainly not be easy. They will, in essence, be trade negotiations in which it is ascertained how we do business with one another in the future."
British Prime Minister Boris Johnson, who pushed through Brexit, said in an address to the nation that its departure was inevitable.
"For all its strengths and its admirable qualities, the E.U. has evolved over 50 years in a direction that no longer suits this country,” he said, adding that going it alone would allow the government to "unleash the full potential of this brilliant country.
Like other European leaders, the European Commission's president, Ursula von der Leyen, strongly disagreed.
"Our experience has taught us," she said, "that strength does not lie in splendid isolation, but in our unique union.”