North and South Sudan are at war. The reasons for the conflict are complex, but the solution is not: To stop the killing, the international community must arm South Sudan. Unlike interventions in Afghanistan and Iraq, the United States need not fire any shots. Just as we have provided weapons to support Israel but never put our own troops at risk, we can help bring peace to this region. We need only make sure that, for the North, attacking the South is a little bit harder than shooting fish in a barrel.