My favourite quote about Woodrow Wilson comes from one of my favourite historians, Walter McDougall. McDougall puts in the mouth of Wilson, the progressive hero and the architect of the idealistic League of Nations, the words of Jesus in Matthew 10:34: "Think not that I am come to send peace on earth: I came not to send peace, but a sword.".
If you understand that, you understand a great deal of American foreign policy in the twentieth and early twenty-first centuries.
Wilson was the first president to argue that the American people had to make real sacrifices for the sake of people on the other side of the planet, and the first to argue that only by doing so could Americans continue to enjoy security and prosperity. When he dispatched American men (not quite boys: back then, the average age of a soldier was 25 - so perhaps not quite men either) to participate in World War I, he started a long tradition which would see millions of American soldiers come back to Europe again, and to Asia, and the Middle East, and almost everywhere else - all for the sake of the ideas that this progressive hero championed.
By deciding to fight Germany, Wilson was the first American president to act forcefully on the idea that the United States could only continue to be a liberal, democratic nation when it existed in a world where the most powerful states also shared its values. What he feared most was a steady collapse of the other democratic states in the world leading to the ascendancy of undemocratic states like Imperial Germany. If that happened, then he feared the United States would have to turn itself into an armed camp and sacrifice its own basic freedoms to maintain a large military and a careful state of watchfulness. It was the first instance of the "domino theory".
It was the classic liberal fear of the military-industrial complex combined with a fear of the conditions that made a military-industrial complex necessary; it led, ironically, to the creation of the complex to try to stop the conditions coming about anyway. Wilson was the first president who told Americans that their own security depended on the security of the rest of the world - the first president to suggest that the bad guys lurking in in Europe or Asia could very quickly come knocking on their own doors. It was truly a small step to trying to "police" the jungles of Vietnam or "spreading democracy" in Iraq.
Even Wilson's most liberal ideas, such as the League of Nations - which was a forerunner of the United Nations - were based on the same assumptions. Wilson wanted an organization that would "make the world safe for democracy" and hoped he could find a way for diplomacy to contain the undemocratic states and stop events like World War I happening again. His vision of negotiated management of foreign affairs failed, but his passionate belief in the importance of democracy overseas lived on. For Europeans like me, this was fortunate - America intervened again in Europe in World War II, gently cajoled into doing so by another liberal president who believed that democracy in America could not survive without democracy being protected overseas.
Wilson wanted, as I said, to "make the world safe for democracy". Some of his successors, and their neoconservative advisors, wanted to make everywhere democratic. The basic ideas were not dissimilar - once it was accepted that the security of the United States rested on stopping the emergence of powerful, undemocratic powers dominating the rest of the world, it was not so great a leap to this sort of zeal. Now the United States faces a rising China which may yet pose a challenge to the sort of liberal international order the Wilson and his successors have believed is vital to the security of the United States. They will be bearing that sword in mind.