BALTIMORE, Md. — For more than two decades, Ukraine has been unable to conduct an independent foreign policy because of its closely integrated and highly corrupt energy ties to Russia. Ukraine’s poorly coined “multi-vector foreign policy” was the outcome of Russian blackmail blocking the country’s long declared strategic objective of integration into Europe.

Editor's Note: Nicholas Burns is GlobalPost's senior foreign affairs columnist. He writes a bimonthly column on the international issues that shape our world.

CAMBRIDGE, Ma. — President Obama’s meeting in California last weekend with the new Chinese President, Xi Jinping, could turn out to be one of the most pivotal of his presidency.

Washington and Beijing billed the summit as an opportunity for the two leaders to get to know each other in the relaxed setting of the late Ambassador Walter Annenberg’s Sunnyland estate.

NEW YORK — We remember the weapons they used. Whether fertilizer or box cutters or pressure cookers, certain objects have become icons for the worst terrorist acts lodged in this country’s history. But one kind of weapon stands out for its spectacle, violence and implications.

The bomb, says Professor Pete Kraska, represents “who [the attackers] were, the type of killing that took place.” It taps into our collective fear of random violence that we hear about in other countries but do not expect in the United States.

DENVER, Colo. — Ever since the dissolution of the Soviet Union in 1991, Russia has fallen from grace and power, and been derided as “upper Volta with nuclear weapons.”

Gone are the glory days of historic victories in World War II, followed by four decades as a superpower challenging the United States for world leadership.