WASHINGTON, D.C. -- Most American presidents are reluctant warriors. Abraham Lincoln spoke of the onset of the Civil War in the passive voice in his Second Inaugural Address. ("And the war came.") Woodrow Wilson waited until the escalation of German submarine warfare before committing to World War I, nearly three years after the conflict commenced in Europe. And Franklin Roosevelt did not enter World War II until two years after it began -- and then not until Pearl Harbor.By now you have probably ascertained this is a column about the terrible choices Obama faces as Vladimir Putin flexes his muscles and thrusts Ukraine -- once known as the bread basket of Central Europe, critically defined as the largest country completely within the borders of Europe -- into crisis.The lessons are difficult to discern:-- The Sudetenland.