For the Islamic State, the jihadi group based in Iraq and Syria that has seized major cities and towns in northern and central Iraq in recent months, slaughter and the fear of slaughter are the coin of the realm. And so far, it's working. Murder is their answer to anyone who doesn't share their twisted vision of their faith. They brand as apostates and worthy of slaughter fellow Sunni Arabs who are uncomfortable with beheadings and torture for breaches of the group's version of Islamic law. The reserve special hatred for Shiite Muslims, promising their own version of the Final Solution for them. And in areas under the control of IS (known as ISIS until recently), Christians were given a simple choice last Thursday: Pay a fortune in protection money, convert, or die. That same demand has been made of other faith minorities in northern Iraq. And to show they mean business, the militants have been scrawling the Arabic letter "N" for "nasrani," a pejorative for "Christian," on the homes of the people they're determined to wipe out. How successful has their terror campaign been? Since June, more than 408,000 Iraqis have been displaced -- the same number of people who fled their homes in the first five months of the year. Almost all of the recent victims have been a result of the IS-led offensive in Nineveh and Saladin provinces. The people displaced in the first five months of the year were mostly from Anbar Province. That is where IS and its local allies began their offensive before expanding it in the north, bolstered by their fighters pouring across the border from Syria, where they've been both fighting the government of Bashar al-Assad and other rebel groups. "Being a Turkman, a Shabak, a Yazidi, or a Christian in ISIS territory can cost you your livelihood, your liberty, or even your life," Human Rights Watch's Middle East Director Sarah Leah Whitson said in a statement. This is all driven by the jihadis' ideology, and should hardly come as a surprise. In their version of Islam, the best that Christians can hope for is to be treated as second-class citizens. But the ultimate objective is to wipe them out, along with all others who stand up to them. Consider how the militants handled the town of al-Alam, southeast of Mosul. Local militias had put up a spirited resistance to the jihadis in June. As Reuters tells it, the movement came up with a brutal solution to the problem. The near-total destruction of Iraq's ancient Christian community, almost as old as the faith itself and with some branches using Aramiac (the language of Jesus) for their liturgy, is not new. The US-led invasion of Iraq unleashed perhaps the greatest challenge to the faith in Mesopotamia for centuries. In the brutal civil war that broke out in the country soon after, minorities of all kinds were targeted, and most estimates are that a pre-war Iraqi Christian population of about 1.5 million people was cut in half by 2009, with targeted assassinations on Christian leaders and terrorist attacks on churches leading to a mass exodus from the country. Three years ago, Iraqi-American Christians warned that in a letter to Vice President Joe Biden that the situation was due to get worse. The response was not encouraging. "Basically, we got a letter back saying: Iraq is undergoing a great democratic process and we should take advantage of that," Robert Dekeileta, a lawyer who volunteers with the Chaldean Assyrian Syriac Council of America, said at the time. "It doesn't take into account that democracy for us is a little bit frightening because a lot of forces in society are opposed to non-Islamic entities like ours." Democracy is the furthest thing from the minds of people living in areas under IS control at the moment. In Mosul -- Iraq's third-largest city and now under the group's control -- the Christians are all gone. In 2003, the city was home to about 40,000 Christians. By 2009, their numbers had dwindled to a few thousand. Since last Thursday, the remaining Christians fled. The horrific reality of the jihadis vision of a "caliphate" couldn't be more clear -- and that's one reason they'll probably ultimately fail. While Iraqis are terrified of IS for now, the IS brand of systematic brutality is likely to ultimately see the Iraqi Sunni Arab community it claims to protect and support turn on it, much as Sunni Arab Iraqis turned on its previous incarnation a few years ago. Many of their battlefield successes have been driven by Sunnis who hate the Shiite-led government in Baghdad and served in Saddam Hussein's old Iraqi army. These Iraqis aren't interested in being under the thumb of an Al Qaeda-style group and are likely to turn on their erstwhile allies as they find IS is more of an enemy to their way of life and beliefs than Iraq's Shiite majority. But in the meantime, the rights abuses of IS are certain to pile up. And when it's over, a 2,000-year-old Christian community will probably be gone for good.