Alexandre Ribot (1842-1923), French PM March-September 1917, and architect of King Constantine’s deposition.

May 28 1917, London--The Allied governments had long had issues with Greece's King Constantine, the Kaiser's brother-in-law.  Matters nearly came to a head in December 1916, when Allied soldiers became involved in a firefight on the streets of Athens.  Sarrail had long been advocating for removing King Constantine entirely, but the French government stopped short of doing so in December, instead demanding concessions and imposing a blockade until they were granted, while simultaneously granting more recognition to Venizelos' government in Salonika.

By May 1917, however, the situation had changed.  Briand's government had fallen, and his replacement as French PM, Ribot, was more open to removing King Constantine.  The revolution in Russia and the deposition of the Romanovs meant that the Russians were no longer as opposed to the removal of King Constantine as an affront to monarchy in general; furthermore, as Russia was in favor of a peace without annexations, Greek ambitions on Turkey were less of a threat.  In Greece, Venizelos was eager to dampen growing republican sentiment among his supporters, and saw a deposition of King Constantine as the only way to preserve the monarchy.

The last piece fell into place on May 28, when Ribot, at a conference in London with Lloyd George, convinced the latter to sign onto the idea as well.  A diplomatic mission would be sent to Athens, notifying King Constantine that his absolutist rule, in supposed violation of the Greek Constitution, would no longer be tolerated by the powers that guaranteed Greek independence.  The demand would be backed by force; Allied troops would soon land around Athens, while a division would move south from Salonika into Thessaly.

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