The Post’s Robert Kagan, a senior fellow at the Brookings Institute, is out with a new book, The World America Made. At a time the president is slashing defense spending, Iran creeps closer to nuclear-weapons capability, and the administration has touted its “leading from behind” notion, Bob looks at the U.S. role in the world and what happens when the U.S. retreats from that historic role. (Bob is an adviser to the Mitt Romney campaign, but the ideas in his book and in his answers below are his. That said, it is useful to hear the sort of advice Romney is likely hearing.)

It is amusing that the Obama administration latched on to part Bob’s thesis — that America remains a great power — but failed to grasp that Bob’s book is in many aspects an implicitly damning takedown of an administration that has tried not to lead, slashed defense spending, excessively relied on multilateral institutions and failed to formulate a coherent policy on democracy promotion. In short, Bob argues that decline is a choice; Obama, unfortunately, seems to be choosing it.

Why did you write the book?

I’ve been worried that many people seem complacent about the prospect of American decline. They think it is both inevitable and tolerable. The vision of the post-American world painted by people like Fareed Zakaria looks very comforting — it looks like we still get to have widespread democracy and a liberal economic international order. The point of my book is that the present world order depends on American power and influence and will not survive American decline. Moreover, there is nothing at all inevitable about American decline. The U.S. is by all reasonable measures as strong as ever. But Americans can choose decline, in the sense of weakening themselves through defense budget cuts and turning inward, giving up on the role they’ve played for the past few decades.

Can we remain influential in the world while drastically reducing military spending?

Obviously not. Both former Secretary of Defense Robert Gates and the current secretary, Leon Panetta, have warned of the disastrous consequences of further cuts. American military power provides the basis of much of the world order. American naval dominance supports the open trading system. America’s ability to project power to distant theaters provides stability and security for allies in those theaters — in Asia, the Middle East, and Europe. What kind of “pivot” can we make to Asia if we are unable to have the wherewithal to provide the reassurance our allies in Asia are looking for?

What is wrong with relying on multilateral institutions to exert leadership?

Multilateral institutions are important tools and multipliers of power. They are not substitutes for American leadership. Institutions like NATO don’t work without American leadership. And, of course, the U.N. Security Council has become paralyzed by the split between the democracies on one side — the U.S., U.K. and France — and the autocracies of China and Russia on the other. That has weakened the world’s ability to act in Syria and Iran in ways more likely to avoid war. Russian and Chinese obstruction makes conflict in Syria more likely to descend into civil war, and it brings the world closer to danger in Iran.

Can you exercise soft power without hard power?

One of the things Americans lose sight of is that there have been many periods in America’s past when the U.S. was not popular, the U.S. system was not beloved and U.S. foreign policy was detested in many places. No one remembers when President Eisenhower was prevented from traveling to Japan because the Tokyo government couldn’t guarantee his security against students protesting against American “imperialism.” Not many people recall that Eisenhower’s vice president was spat on and attacked in Caracas in protest against the American-orchestrated overthrow of Jacobo Arbenz in Guatemala. That did not mean the U.S. wasn’t powerful in that era. And American power, then and now, stemmed to a large extent from its ability to deploy hard power to protect nations worried about their neighbors. Of course, soft power is important, but it must be supplemented by hard power. In fairness to Joe Nye, who invented the term “soft power,” he has always made this point himself.

What is the role of democracy promotion in a successful U.S. foreign policy?

The spread of democratic governments has been an essential attribute of the American world order. Whatever specific interests have been sacrificed, achieving Americans’ broader interests in a more peaceful world and a more open economic system has compensated. It is demonstrably true that democracies rarely go to war with other democracies and that politically liberal regimes are more likely to favor liberal economic systems. Americans’ enduring interest in a liberal world order generally transcends other, more narrow and temporary, interests. The United States can lose an Egyptian ally but still gain a healthier world order. That is probably why Americans have sometimes chosen to support democratic movements and sometimes only purportedly democratic movements, even when their immediate interests might argue against it.