“If you do not leave these areas urgently, you will be annihilated. … You know that everyone has given up on you. They left you alone to face your doom, and nobody will give you any help.”

These chilling words come from leaflets dropped over the besieged area of Aleppo by Syrian and Russian aircraft, before the final bloody assault on the city. And during the last few days, they have rung truer than anyone in Aleppo, or anywhere else, had dared to imagine.

But the warnings were there, and not just in the form of leaflets. After five years of war, the world can’t claim it lacked information about the Syrians’ desperate need, or opportunities to respond.

Eastern Aleppo is now the epicenter of the Syrian conflict, forced to endure wave after wave of ferocious bombardment that threatens to reduce it to a pile of broken concrete and dust. With the pro-government forces’ latest push to seize control of the area, the conflict has turned more bitter and bloody than ever before. In a matter of days, Syrian government forces advancing on eastern Aleppo have captured new territories held by armed opposition groups, including the districts of Jabal Badro and Masaken Hanano, where at least 100 families are living. Since Nov. 25, the U.N. Office for the Coordination of Humanitarian Affairs reported that 25,000 people have fled the besieged area.

Some of the area’s beleaguered residents have given up all hope of international action to halt their suffering. “There is nowhere to run or hide,” said one resident, Nizar. Before the latest assault, in anticipation of the renewed bombardment, another resident, Um Mohamed, said she felt it was only a matter of time “before hell is unleashed again.”

With callous disregard for civilian lives and international humanitarian law, Syrian government forces and their Russian allies have used massive firepower to inflict maximum human suffering, destroy civilian infrastructure, and impose a crippling starvation siege on the area.

Residential buildings, hospitals, medical clinics, and schools have been repeatedly targeted in unlawful attacks. The attacking forces have used barrel bombs and internationally banned cluster munitions, in many cases amounting to war crimes. The threat from aerial attacks is so intense it has forced the residents of Aleppo to eke out an existence in a warren of underground safe houses.

Scores of hospitals in Aleppo have been targeted during the past year, most recently a children’s hospital in the al-Shaar neighborhood last week. In March, Amnesty International documented how medical facilities in opposition-held areas around Aleppo have been targeted as part of a military strategy to empty areas of residents in order to facilitate a ground invasion.

As thousands of civilians have poured out of eastern Aleppo, many of those left behind live in fear of arbitrary arrests, torture, or enforced disappearance by government forces. Around 8,000 people have fled to the Kurdish-controlled area of Sheikh Maqsoud because they are too scared to flee to government-held areas.

In the face of devastation and suffering on such a massive scale, the world has time and again failed to help civilians in eastern Aleppo.

In the face of devastation and suffering on such a massive scale, the world has time and again failed to help civilians in eastern Aleppo. This is emblematic of the impotence of the international community, which has repeatedly failed to do anything to stop rampant abuses and violations of international law as the Syrian catastrophe has worsened over the last five years.The U.N. Security Council has been held hostage by Russia, which has repeatedly used its veto to shield the Syrian government. During the past five years, Moscow has vetoed five resolutions that sought to end some of the horrific abuses and to bring to justice those responsible by referring the situation to the International Criminal Court. Just last month, Moscow vetoed a resolution aimed at ending airstrikes and bloodshed in Aleppo.

The two U.N. Security Council resolutions, 2139 and 2165, that eventually were approved demanded unfettered access for humanitarian relief, the lifting of sieges on the city, and an end to attacks on civilians, torture, and enforced disappearances. They have, however, been flouted on a daily basis with no consequences for the perpetrators. And even when it hasn’t been used outright, the threat of Russia’s veto power has been enough to paralyze the Security Council and prevent it from imposing targeted sanctions on Syrian government officials for not complying with the two resolutions.

U.N. officials and world leaders have expressed shock and outrage at the continuing bloodshed. But the people of Aleppo need more than their words of condemnation.

To stand any real chance of ending crimes against humanity in Syria, concrete measures are needed — such as sanctions that target officials who have ordered unlawful attacks, a comprehensive arms embargo to stop the flow of weapons to the Syrian regime, and a means of bringing perpetrators of war crimes to justice.

A Security Council decision to refer the situation in Syria to the International Criminal Court would at the very least signal that those responsible for Syria’s atrocities will not go unpunished. Absent such steps, these horrors will continue to proliferate not just across Syria, but across the globe.

The cruel betrayal of eastern Aleppo’s civilians will be a stain on the world’s conscience for years to come. Nothing can make amends for the failures that have led to global inaction on this catastrophe. The least we can do is to try to ensure that the horrors they have endured are not allowed to happen again.

AMEER ALHALBI/AFP/Getty Images