Iraq's Sunnis long have complained of discrimination and abuse since the 2003 U.S.-led invasion that toppled Saddam Hussein's Sunni-led dictatorship and replaced it with a government dominated by the country's Shiite majority. The Iraqi forces there, including its vaunted special forces units, slipped out of the city, leaving Sunni tribesmen armed only with light weapons and their personal vehicles to battle the extremists, they said. A senior Iraqi intelligence official and operations commander in Anbar province confirmed that counterterrorism forces were the first to pull out of Ramadi, abandoning 89 Humvees and armored cars, as well as rifles and mortars. Yet despite being targeting by the Islamic State group, many of the Sunni tribesmen from Anbar who spoke to the AP said the Baghdad government viewed them as being complicit in the extremists' advance, solely because they share the same sect. Hameed al-Zerjawi, Iraq's secretary-general for national security, said the American advisers will work with Iraqi security forces, which then will train militia fighters. The government-backed fighters, made up predominantly of Iranian-backed Shiite militias, now outnumber Iraqi security forces in all of Iraq and are considered the most effective fighting force on the ground today. [...] while the Popular Mobilization Forces insist they aren't sectarian, human rights groups have accused individual Shiite militias fighting within the structure of harassing or attacking Sunni civilians, as well as destroying their homes and businesses.