The world’s best-known street artist, Banksy, has teamed up with Oxfam and other groups this week to highlight the third anniversary of the conflict in Syria. Of course, the anonymous British provocateur is much more than a graffiti artist—his playful, confrontational stencils have become iconic online and in print, too, challenging us to redefine the limits of the genre.

Banksy’s new graphic, a reworking of his famous image of a girl holding a red, heart-shaped balloon, evokes a sense both of hope and of loss. It’s an appropriate image at a time when the crisis in Syria has reached staggering proportions. More than 100,000 people have been killed. Millions more have been driven from their homes. Oxfam is helping more than 900,000 people across Syria, Lebanon, and Jordan with lifesaving essentials, but the needs of families remain enormous.

Still, hope for peace remains strong. This week, Syrian voices have joined a coalition of more than 50 humanitarian and human rights groups from all over the world—including Oxfam, Save the Children, Amnesty International, and the International Rescue Committee–to simultaneously call on world leaders to commit to making this the last anniversary marked by bloodshed.

The campaign, which uses the hashtag #WithSyria, calls for urgent action to ensure that Syrians in need (including civilians in areas under siege) can access aid. Oxfam’s also calling for the voices of ordinary Syrians to be heard and heeded in reconvened peace talks.