This month marks 65 years since the successful conclusion of the Berlin Airlift, and the anniversary has provided supporters of a tougher U.S. line on Ukraine a useful analogy. The U.S. resupplied Berlin in 1948-49, the argument runs — why can't it offer Kiev more support today?

Probably it could; possibly it should; but first it's important that we understand the lessons of history.

For critics of President Barack Obama's policy in Ukraine, the analogy is obvious. The historian Thomas DiBacco reminds us that the polls of six decades ago showed a strong American willingness to sacrifice at home in order to help Berlin. These and similar arguments reflect the familiar complaint that U.S. power and influence have declined, and that the current administration's foreign policy is indecisive and risk-adverse. Whether or not the criticism is apt, it's important to recall that in 1948, a war-weary U.S., with its armed forces much reduced, saw the airlift as no more than a stopgap.