1921: The first aircraft carrier is commissioned.

Today: During periods of threatened conflict, aircraft carriers supply off-sea staging areas for bombing runs. They greatly add to a country's ability to wage war.

1921: The Russian economy collapses, and Russian sailors attempt a bloody and unsuccessful mutiny.

Today: The economy of what was once the Soviet Union is in disarray, creating increased risk from an unpaid military establishment.

1921: Poliomyelitis (polio) is widespread in North America; it attacks U.S. Secretary of the Navy, Franklin Delano Roosevelt, and will leave him crippled for life.

Today: Polio is almost completely eradicated due to immunizations, but as each disease is cured, new ones appear to take its place.

1921: Famine kills 3 million Russians, and corpses are piled twenty feet high waiting for burial.

Today: Famine continues to be a leading cause of death in the world as a result of weather...