On 11/11/1918, the armistice that ended World War I came into force. A century later, an American president talks wistfully about nationalism and a return to the international relations practices of the 19th century--two ingredients that made World War I possible. 1/x 
A century later, we know the toll of that war: an estimated 40 million military and civilian casualties; including 15 to 19 million dead. 2/x
The failure to achieve a meaningful and lasting peace after the armistice led to the Second World War and another 60 million dead. 3/x
But in the First World War--the war to end all wars--industrial warfare outpaced tactics and the battle fields became meat-grinders. 4/x
At the Battle of the Somme in 1916, British and French forces suffered more than 600,000 casualties. German forces suffered between 465,000 and 600,000 casualties. This was slaughter. 5/x
Let's talk in terms of big round numbers: 6/x
Russia mobilized 12 million men. 76.3% were killed, wounded, missing, or captured. 7/x
The British Empire mobilized 8.9 million men. 35.8% were casualties. 8/x
The French mobilized 8.4 million men, 73.3% of whom became casualties of war. 9/x
The United States, late to the war, mobilized more than 4.3 million troops. It's casualty rate was about 7.1% 10/x
Among the central powers, Germany mobilized 11 million troops, and suffered a casualty rate of 64.9%. 11/x
Austria-Hungary shredded its military in the war triggered by the assassination of the heir to its thrown. They mobilized 7.8 million troops who suffered a 90% casualty rate. 90%. 12/x
If you were a young man in Europe during the war--and by young, I mean 15 to 49, you likely served in it. In France, the demands for manpower meant that 80% of the male population between 15 and 49 years of age served in the military. 13/x
The paradoxical forces of nationalism--driving some people together and others apart--contributed to the outbreak of the war, along with arms races, domestic politics, and military planning that emphasized the need to strike fast at the outset of any war. 14/x
But when the guns fell silent, leaders of the victorious allies set out to make sure war would never happen again. For U.S. President Woodrow Wilson this meant an idealistic, internationalism under-girded by the new League of Nations. 15/x
For the leaders of France and England, avoiding a future war meant keeping Germany down--and the terms of the treaty they ultimately negotiated punished Germany for the war. 16/x
By the time the dust settled, the British seemed remorseful for the terms they won at Versailles; the U.S. failed to ratify the treaty and returned to isolationism. And France found itself alone, again, on a continent with a revanchist Germany. 17/x
To say that the seeds of World War II were sown in the wake of World War I is to state the obvious. 18/x
But it is just as important to recognize that nationalism and a belief that power, above all else, was the final arbiter of international relations, contributed to the outbreak of the war. 19/x
This is why Wilson sought to construct a new international system after the war. 20/x
ilson failed, but one generation later, the victorious allies tried again to build an international system that would manage conflict and operate on international law and not the law of the jungle. 21/x
So as we grapple with the utterances of an American president who proclaims himself a "nationalist," and adopts an approach to international relations more apt to the era before 1914, let's remember the cost of the First World War and pray that there's never a third. 22/22
