Some time this spring, the death toll in Syria’s grinding war surpassed 400,000.

The number is an estimate. War is always chaotic, but Syria’s war is chaos incarnate. The government — the Assad dictatorship — attacks civilian neighborhoods with chemical weapons. ISIS, which still controls significant territory, razes captured towns and uses mass murder as a strategic political weapon. Russian aircraft, allegedly attacking ISIS, bomb any target the Kremlin deems useful. Collateral damage and dead innocents? Western peacenik denunciation has no effect on Moscow.

Other international interlopers spill blood. Iranian Special Forces and Lebanese Hezbollah thugs attack anti-Assad rebel enclaves. Turkish artillery occasionally fires on ISIS positions in Syria. In odd corners and for opaque reasons, renegade and sectarian gunmen battle neighborhood militias. U.S. aircraft occasionally drop bombs. Washington recently acknowledged American Special Forces operate in Syria. See, the U.S. allegedly leads President Barack Obama’s so-called anti-ISIS coalition.

Observers attempting to confirm body counts in the hodgepodge madness confront another problem: the Assad regime habitually lies about the number of dead and wounded.

In such a war, accurate casualty figures are understandably difficult to obtain.

However, several analysts think 400,000 dead is a credible guess. The war began in late February 2011. By December 2011, 70,000 had died. In Spring 2014, as ISIS invaded Iraq, 250,000 dead was a common estimate. In December 2015, the Syrian Center for Policy Research claimed the toll was 470,000. High? Perhaps. On April 22, U.N. Special Envoy to Syria, Steffan de Mistura, said he estimated 400,000 had been killed. De Mistura noted that for two years the U.N. quit trying to keep accurate numbers.

As a historical comparison, from 1991 through 1996, civil and ethnic warfare in disintegrating Yugoslavia killed some 200,000 people. Yugoslavia’s combat and slaughter was bitter, but more episodic than Syria’s. U.N. peacekeepers were deployed. Arguably, their presence tempered violent excesses, as they provided some protection for relief agencies and patrolled supply routes. While the peacekeepers certainly couldn’t stop the carnage, medical aid probably reduced civilian casualties, which is why international agencies beg Syria’s belligerents to open humanitarian aid corridors.

On May 6, StrategyPage.com supported the 400,000 death toll estimate while noting that over 60 percent of the dead were killed in a few bitterly contested areas. Twenty percent have been killed in or near Aleppo, “…18 percent around Damascus, 10 percent in the northwest (Hama, Latakia and Idlib provinces) and eight percent down south” (around Daraa and near Syria’s border with Israel).

In Aleppo, pro-Assad (government) forces continue to fight fierce street battles with ISIS gunmen and other Sunni Muslim radicals. Some 400,000 (that number again) civilians remain trapped in Aleppo.

Battles with high casualties occur in almost every war. High casualty numbers concentrated in specific, restricted areas are usually associated with a battle of attrition fought over territory the belligerents will not cede. The areas StrategyPage mentioned are precisely that, especially Aleppo. In a grinding war like Syria’s, they become killing fields.

StrategyPage added that there is evidence that ISIS has executed more than4,200 people in Syria — executed, as in lined up and shot or beheaded or dismembered or burned to death. The executions are often video-recorded. ISIS commanders believe mass executions serve as strategic political propaganda. As for the number of people ISIS gunmen, suicide bombers and artillery have killed in combat and terror attacks? No one really knows.

If we had a Republican president I’m rather certain we’d be hearing demands that the U.S. has a “responsibility to protect” vulnerable civilians. The abbreviation for this policy is R2P. During the Bush Administration the Obama Administration’s current U.N. Ambassador, Samantha Power, was a vocal advocate of R2P. Now? Not so much. History will note the 400,000 Syrian dead died are on her president’s watch.

Austin Bay is a syndicated columnist and author.