SENIOR MILITARY OFFICER: What's Happening In Iraq Is 'Exactly What We Forecasted'

As radical militants continue to seize vast portions of Iraq less than three years after the last American soldiers left the country, some retired U.S. military leaders are pushing the Obama administration to fight back against a nightmare scenario of sectarian violence many believed was inevitable.

"We said we won some success but this is reversible," a retired senior U.S. military officer told Business Insider on condition of anonymity. "So what we're seeing now is exactly what we forecasted."

Extremists from Islamic State of Iraq and Syria (ISIS) have captured key cities, including Fallujah, Tikrit, and Mosul, while Kurds have taken the oil-rich city of Kirkuk - with many wondering whether Baghdad comes next.

While the White House rebuffed a request for air support from Iraqi Prime Minister Nouri al-Maliki last month, the Obama administration is under increasing pressure to do something as Tehran's influence seems to be quickly replacing Washington's.

"The U.S. will have to act to stop this onslaught," retired Marine Gen. John Allen, the former commander of coalition forces in Afghanistan in 2011, told Defense One's Stephanie Gaskell. "We have an obligation, and indeed we have the capability, to help now."

On Thursday, Obama signaled that he was prepared to act militarily, telling reporters he wouldn't "rule out anything." But with much talk and little action seen to quell a four-year-old civil war in Syria, a retired senior U.S. military officer told Business Insider there was little hope of U.S. action besides a possible weapons transfer of small arms.

"The western democracies do not have the political will. They don't have the leadership, they don't have the rationale, they just don't have what it takes," the officer said, frustrated at a situation he believed was avoidable. "The reason Assad is still in power is he has the better ally [in Iran and Russia]."

What happens next is hard to predict - especially as Iran sends in its elite Revolutionary Guards to help bolster Maliki's government - but one of two scenarios are likely: Iraq's problems mirror Syria's, with a civil war stalemate that continues for years, or a fracturing of the country along religious and ethnic lines of Sunni, Shia, and Kurd, the officer said, adding that it's "gonna get messy."

"The next president, male or female, Republican or Democrat, is not going to be able to overcome all the damage this administration's lack of strategy has caused."