The rapid expansion of the Islamic State of Iraq and the Levant (ISIS) across Iraq is leading to sectarian violence on a scale not seen in the country in years. In June 2014 alone, approximately a thousand Iraqis -- nearly all civilians -- have been killed.

The U.S. is currently sending roughly 300 military advisers to the country and pressuring its political leaders to overcome the sectarian governance under Shi’a Prime Minister Nouri al-Maliki that has created a base of support for ISIS among the alienated Sunni minority.

Former State Department policy director Anne-Marie Slaughter, who is critical of the president’s actions in the region, asks the following question about the U.S.’s perennial neglect of ISIS in a New York Times op-ed piece, “Don’t Fight in Iraq and Ignore Syria:”

Why is the threat of ISIS in Iraq a sufficiently vital interest, but not the rise of ISIS in Syria...?

She attributes the action in Iraq but the inaction in Syria to the administration’s bipolar thinking: the U.S. is re-engaging in Iraq because the threat of ISIS exists on the urgent plane of “national security,” while the bloodshed in Syria, which has claimed over 140,000 lives, is a humanitarian disaster in which no American interests are at stake.

In disagreement, Slaughter concludes:

In fact, the two planes are inextricably linked. When a government begins to massacre its own citizens, with chemical weapons, barrel bombs and starvation, as Syria’s continues to do, it must be stopped. If it is not stopped, violence, displacement and fanaticism will flourish.

Her observations beckon an investigation of the Syrian civil war, America’s involvement in it -- or lack thereof -- and how America’s policies are connected to the destabilizing effects that are rippling across the borders of numerous countries -- borders that ISIS hopes to erase in order to construct a transnational Islamic state.

The conflict in Syria began in March 2011 on the heels of the Arab Spring. Disillusioned members of Syrian president Bashar al-Assad’s military defected and created the Free Syrian Army (FSA) under the guidance of the Supreme Military Council (SMC), headed by Gen. Salim Idris.

In the initial months and years of the conflict, the FSA and the Syrian military traded control of cities and neighborhoods of the country’s largest cities, including Deraa, the capital Damascus, Homs, Hama, Latakia, and the country's most populous city, Aleppo.

On several occasions, President Obama declined the advice of the FSA and top national security advisers to send arms in order to tip the balance. Instead, the State Department initially offered hundreds of millions of dollars in humanitarian aid to help displaced Syrians and has provided non-lethal aid, including logistical equipment and basic provisions, such as food and medicine.

Though President Obama announced that Assad “had to go” shortly before the 2012 election, he

declined a plan approved to by top national security advisers to arm SMC-affiliated rebel groups.

In June 2013, however, the White House authorized the CIA to ship light weaponry and ammunition through Turkey.

Because of logistical difficulties, the shipments did not arrive until September 2013 -- at the same time when President Obama called for airstrikes against Syrian military facilities in response to the chemical attack in Damascus a month earlier.

During this tense period in mid-September, foreign jihadists -- who on some occasions cooperated militarily with the moderate fighters against Assad's forces -- started to noticeably eclipse the power of moderate groups.

On the 12th anniversary of the September 11 attacks, al-Qaeda leader Ayman al-Zawahiri declared that the FSA was “the enemy of Islam." On the following day, affiliates of al-Qaeda, including ISIS, commenced operation “Expunging Filth” against the moderate rebels.

One ISIS defector, calling himself K. in one interview, recalls that the group began “hunting infidels house by house, or…ruin by ruin.” It was at this point that K. realized that his goal of deposing and replacing Assad did not match the long-term strategy of ISIS:

Our priority was Aleppo. We repeated that we had to advance from north to south — Aleppo, Hama, Homs, down to Damascus — and they replied that the priority was to deprive the regime of the bulk of its economy — of Raqqa and Deir Ez-Zor, which have oil and agriculture.

K. concludes: “Now I realize that they didn't come for Assad."

Instead, ISIS focused on eastern Syria.

The moderate rebels' waning military strength caused thousands of individual fighters and even entire city-specific brigades to abandon the moderates -- militarily and politically.

Later that month, 13 Islamist groups renounced their support for the largest political opposition group, the Syrian National Coalition (SNC). Many brigades that had formerly allied with the FSA founded a rival organization, the Islamic Front. Some of these brigades support ISIS.

The growing divisions among the rebel opposition gave President Assad a position of strength going into the Geneva II peace talks in early 2014.

Following the formation of the Islamic Front, the SNC could no longer claim to legitimately represent the Syrian people, and the rebels’ internecine fighting and military losses gave the SNC little leverage in its demands for a transitional government and a post-Assad future. Assad also claimed that, in his absence, the country would be overrun by terrorists.

The Geneva II talks produced no tangible results.

In the meantime, ISIS swept eastward across Syria, capturing lucrative oil fields and even selling electricity from power plants under its control to the Syrian government.

ISIS has roughly $2 billion in assets with which to finance its recrudescence in Iraq and its operations in Syria.

In June 2014, ISIS launched a blitzkrieg across Iraq, capturing the cities of Tikrit and Mosul and progressing rapidly toward the capital Baghdad.

The American military advisers are set to arrive in Iraq in late June. The Maliki government has requested the use of drone strikes against ISIS, which the president has not ruled out. President Obama did, however, rule out the prospect of redeploying U.S. ground troops, which withdrew from Iraq in 2011.

In a June 2014 interview, the president defended his policy toward the moderate Syrian opposition, claiming it was "a fantasy" to expect that "farmers, dentists," and otherwise inexperienced fighters could defeat both jihadi and Assad's forces and secure the entire country.