As the Islamic State, insurgents, and government forces battle in Syria, the population of Christians there continues to decline, from 1,250,000 in 2011 to less than 500,000 this year, according to ADF International, which advocates for religious freedom worldwide. In a sub-report submitted with the report Genocide Against Christians in the Middle East to Secretary of State John Kerry in March, the ADF International details the ongoing genocide of Christians and other religious minorities in the Middle East. It notes that "Christians are the most persecuted religious group in the world" and that in at least 104 countries Christians are harassed and persecuted by governments and organizations. The harassment includes "physical assaults, arrests and detentions, the desecration of holy sites and discrimination against religious groups in employment, education or housing," reads the report. Harassment of Christians "was the highest in the Middle East and North Africa (90% of countries)," reported ADF International. In Syria and Iraq, the persecution of Christians is carried out largely by radical Muslims, such as the Islamic State and Jabhat al-Nusra, said the ADF. In Syria, government forces have been fighting against revolutionaries and the Islamic State since March 2011, an ongoing battle sparked by the Arab Spring. In 2015, Syria's population was approximately 20 million, said ADF International, and "92.8% of the population was Muslim, 5.2% Christian and 2% other." "The population of Christians dropped from 1.25 million in 2011 to as few as 500,000 today," said ADF International in its report. "It is estimated that in 2015 alone, over 700,000 Christians in Syria sought refuge" in other countries. Persecution of Christians in Syria is extreme, said the ADF International, and includes the following examples: "Three Christian men who were executed for refusing to convert to Islam, a Catholic priest who was beheaded by the rebels, at least 15 Assyrian Christians who were beheaded or shot, three Christians who were executed, and at least 10 people who were ordered executed by a self-proclaimed 'religious court' for being Christian." "In September 2013, 36 Muslim religious leaders issued a fatwa allowing Sunni Muslims to seize the property belonging to Christians or other non-Muslim religious groups. Numerous Christians and Christian religious leaders became victims of kidnappings. Greek Orthodox Archbishop Boulos Yazigi and Syrian Orthodox Archbishop Yohanna Ibrahim are still missing. "In September 2013, Al Nusra attacked the predominantly Christian town of Maaloula, killing 20 people, abducting 15, and destroying Christian religious places. No Muslims were attacked. "In October and November 2013, over 1,500 families in the Christian village of Sadad were being held hostage by Al Nusra. 45 people were killed. "In October 2014 Franciscan Father Hanna Jallouf and 20 Christians were kidnapped by Al Nusra. They were eventually freed. "In January 2015, it was reported that the Armenian Catholic Father Michel Kayyal and Greek Orthodox Father Maher Mahfouz were killed. "In February 2015, IS [Islamic State] seized 35 Assyrian Christian villages, kidnapping over 300 Christians. IS released 23 people in March 2015 and demanded