BETWEEN 1936 and 1939, the Spanish Civil War condensed the awful drama of the 1930s into one conflict. Spain was where left-wing illusions about Stalinism went to die, where Hitler’s war machine tuned up for the Blitzkrieg, where aerial bombardments of civilians and politically-motivated “cleansing” were normalized. It was a proxy war for the totalitarian powers, a magnet for volunteers from around the Western world, and an object lesson in the impotence of Europe’s liberal democracies.

As with Spain, so now with Syria. Once again we have a divided country bled by an ideological proxy war — this time between the Salafism of the Gulf states and the Twelver Shi’ism of the Iranian regime, with other regional and global powers hovering in the background. Once again we have the escalating atrocities — chemical warfare, massacres and religious persecutions, the return of beheadings, slavery and crucifixion. Once again we have ideologically motivated volunteers rushing in from far and wide; once again we have liberal powers seemingly helpless to bring the conflict to an end.

But then there is this illuminating difference. The Spanish Civil War actually ended relatively swiftly; after less than three years of fighting Franco’s nationalists had won. The Syrian conflict, though, is in its fifth year and counting, and its ultimate outcome is no clearer today than it was in 2012 or 2014.

In part, this difference is actually a grim sort of good news — not for Syria, obviously, but for the world. One reason Spain’s civil war ended quickly was the sheer effectiveness of the military aid the Axis powers sent to the nationalist cause. Spain proved (or seemed to prove) the effectiveness of total war as a tool of ideologically-motivated statecraft: The left was crushed, Franco’s regime established, and looking from afar Adolf Hitler could draw an obvious lesson for his own terrible ambitions.