Last week, on August 3, Iraqi Yazidis marked a bitter anniversary. Two years ago, ISIS fighters drove off Kurdish Peshmerga militiamen defending the Yazidi town of Sinjar and took control. The ISIS force quickly killed 2,000 Yazidi men. All told ISIS fighters would massacre some 5,000 Yazidi men in the Sinjar region. A systematic campaign of rape and enslavement followed the massacre. War crimes, crimes against humanity? Yes, but not according to ISIS-aligned Muslim clerics. According to ISIS clerics, Yazidis are pagan heretics -- they worship a peacock or fire angel -- so rape, enslavement and, yes, death? All are justified. In military terms, the ISIS battle group that attacked Sinjar was seeking to secure what ISIS called its "sanctuary area." Sinjar is located near the Syria-Iraq border, northwest of Iraq's second largest city, Mosul. ISIS seized control of Mosul on June 10, 2014 and later proclaimed it the capital of its global caliphate. The Kurd militias northwest, north and to the east of Mosul were lightly armed but still represented a security threat. ISIS commanders wanted to destroy them or drive them away. However, in ISIS ideological terms, securing also means expelling, arresting or killing religious and ethnic minorities. In June 2014, ISIS commanders fired Iraqi Kurds, Turkmen, Shabaks, Christians and Yazidis who had government jobs in Mosul. Christians were given a deadline to convert to Islam. ISIS commanders also executed Shia Muslims -- both Arab and Turkmen -- as a warning to Shias. Think of the French Revolution's Jacobin radicals displaying the guillotine in the public square. The execution of Shias reminded the people of Mosul that ISIS exercised absolute authority. Understand that they live to conquer. The conquest of territory -- the Caliphate -- distinguishes ISIS from al-Qaida. ISIS leaders contend their caliphate is a 21st century extension of Islam's once glorious history of military conquest. In 2014, ISIS leaders bet that conquest would draw recruits. Intentional barbaric excess and terror also served as ISIS recruitment tools. Hideous but true -- ISIS' systematic slaughter of Iraqi Christians (Chaldean-Assyrian) and Yazidis living in northern Iraq was not only ideologically permitted, it was a form of sensational advertising. ISIS not only conquers, it subjugates. Let's return to Sinjar in the first weeks of August 2014. After seizing Sinjar, ISIS forces pursued fleeing Yazidis. Around 50,000 Yazidi refugees fled to Mount Sinjar -- a ridge near the Iraq-Syria border with good defensive positions. However, it has little water and shelter. Upon confronting the mountain's defenses, the terrorists decided to conduct a siege. Starvation and dehydration would kill the Yazidis. ISIS got results. Kurdish and Iraqi sources reported that over a hundred Yazidis are dying each day from thirst and exposure. A Kurdish militia force counter-attacked and tried to open an escape corridor. It failed. However, the anti-ISIS coalition led by the U.S. was able to provide the Kurds with some combat air strikes. Coalition and Iraqi aircraft managed to air-deliver medical and food supplies to the refugees, but the aid was insufficient. This coalition operation attracted major media attention in the U.S. and Western Europe. The Kurdish force eventually broke through. Though the Obama Administration claimed the siege was broken on August 13, suffering refugees continued to trickle out of the mountains for another two weeks. Then the evidence began to trickle out as well, of enslavement and mass rape of Yazidi women after Sinjar's capture. Many of the women were taken as sex slaves and shipped to Mosul or to ISIS camps in Syria. In August 2016, ISIS still controls Mosul. The UN says ISIS continues to subject "every Yazidi woman, child or man that it has captured to the most horrific of atrocities." That means the Yazidi genocide isn't really over.