Robert Zaretsky is professor of history at the Honors College, University of Houston. His most recent books are Albert Camus: Elements of a Life and France and Its Empire Since 1870 (with Alice Conklin and Sarah Fishman).

Words, if not history, are repeating themselves in France. Following the French government's dispatch of planes and troops last week to Mali, whose government is besieged by Islamist rebels, a particular phrase -- l'union sacrée -- has been resurrected. Forged nearly a century ago, those two words nevertheless cast light on the future of France's current military intervention.

When President François Hollande announced last Friday that he had ordered the Mali operation, leading politicians quickly hailed his decision. "Sacred union" immediately became the phrase du jour of the French media. The conservative paper Le Figaro welcomed the "sacred union of the political class" -- a sentiment and wording echoed by the centrist Le Parisien and liberal Le Monde. One of the leaders of the main opposition party, the Union for a Popular Movement (UMP), declared that such a union was "not an option, but an absolute necessity and duty for us all." Even Marine Le Pen, leader of the extreme right-wing Front National, rallied to the government's decision.

This orgy of bonding among inveterate enemies happens to be taking place on the eve of the centennial anniversary of the phrase's birth. The occasion, predictably, was an earlier war -- the war, you may recall, meant to end all wars. On Aug. 3, 1914, President Raymond Poincaré declared that France was going to battle against Germany. "Heroically defended by all her sons," he affirmed, the nation's "sacred union will never be shattered in the face of the enemy."

The phrase lives on, in large measure, because the political, social, and ideological contexts that created it never truly died. Sacred Union 2.0, it turns out, looks a lot like Sacred Union 1.0...