The Islamic State of Iraq and Syria (ISIS) publishes a weekly webzine, The Islamic State Report. The latest issue is headlined “Smashing the Borders of the Tawaghit.” (“Tawaghit” are non-Muslim creations.) ISIS, citing the Sykes-Picot Treaty of 1916 between the British and French, boasts that it is destroying the “partitioning of Muslim lands by crusader powers.” That may seem like a quixotic task for a relatively small band of irregulars, but in trying to redraw the map of Iraq and Syria, ISIS has hit upon a weak link in the chain holding the nations of the Middle East together.

It is easy to blame what is going on in Iraq or Syria on dictators and terrorists, but these various bad actors are bit players in a drama that goes back at least to World War I. What is happening is that the arrangements that the British and French created during and after World War I—which established the very existence of Syria, Lebanon, Iraq, and Jordan, and later contributed to the creation of Israel—are unraveling. Some of these states will survive in their present form, but others will not. The United States may, perhaps, be able to slow or moderate the process, but it won’t be able to stop it.

If you look at a map of the Middle East in 1917, you won’t find Lebanon, Syria, Iraq, Jordan, or Palestine. Since the sixteenth century, that area was part of the Ottoman Empire and was divided into districts that didn’t match past or future states. The British and French created the future states—not in order to ease their inhabitants’ transition to self-rule, as they were supposed to do under the mandate of the League of Nations, but in order to maintain their own rule over lands they believed had either great economic or strategic significance.

In 1916, as The Islamic State Report indicates, the French and British agreed to divide up the Ottoman Middle East in the event that they defeated Germany and their Ottoman ally. The French claimed the lands from the Lebanese border to Mosul; the British got part of Palestine and what would be Jordan and Southern Iran from Baghdad to Basra. After the war, the two countries modified these plans under the aegis of the League of Nations. At San Remo in 1920, the British got the territory that in 1921 they divided into Palestine and Transjordan and all of what became Iraq. (France gave up northern Iraq in exchange for 25 percent of oil revenues.) The French got greater Syria, which they divided into a coastal state, Lebanon, and four states to the east that would later become Syria.

These lands had always contained a mix of religions and ethnicities, but in setting out borders and establishing their rule, the British and French deepened sectarian and ethnic divisions. The new state of Iraq included the Kurds in the North (who were Sunni Muslims, but not Arabs), who had been promised partial autonomy earlier by the French; Sunnis in the center and west, whose leaders the British and the British-appointed king turned into the country’s comprador ruling class; and the Shiites in the South, who were aligned with Iran, and who had been at odds with the Sunnis for centuries. After the British took power, a revolt broke out that the British brutally suppressed, but resentment toward the British and toward the central government in Baghdad persisted. In the new state of Transjordan (which later became Jordan), the British installed the son of a Saudi ruler to preside over the Bedouin population; and in Palestine, it promised the Jews a homeland and their own fledgling state within a state under the Balfour Declaration while promising only civil and religious rights to the Palestinian Arabs who made up the overwhelming majority of inhabitants.