If you'd never heard the acronym AIIB until this week, don't blame yourself.

Strictly speaking, the Asian Infrastructure Investment Bank doesn't even exist yet. But the Chinese-created alternative to the World Bank and International Monetary Fund is turning out to be extremely important. More than 40 countries have applied to join, almost all of them close U.S. allies — and they've applied despite aggressive American efforts to discourage them.

The upstart bank is already emerging as a major foreign policy victory for China, one all the sweeter because it's a direct diplomatic win over the United States.