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Twenty years after the Berlin Wall fell, now unified Germany has a far bigger footprint on the world stage, demonstrating an assertiveness that was unthinkable for most of the post-Nazi period.

Vanquished Germany, cleaved in two by the war's victors, served mainly as a pawn and potential battleground during the Cold War.

For decades, the interests of West Germany took a back seat to those of its neighbors, who still bore wretched memories of World War II. It relied heavily on "chequebook diplomacy" in forking out funds to clear impasses.

"Being European was the only nationalism allowed in Germany," said Ulrike Guerot of the European Council on Foreign Relations.

But after the two Germanys became one in 1990, the country tentatively began flexing its muscles,...