This month marked a grim milestone for Sudan, the unfortunate African country suffering what is considered the world’s worst humanitarian crisis. On April 15, the country’s brutal civil war entered its third bloody year, with an estimated 150,000 people killed, about 12 million displaced and no settlement in sight.

The next day, the State Department for the first time characterized the atrocities being committed in Sudan’s western Darfur region as a genocide, citing the systematic killings of men and boys and the sexual violence against women and girls from the Masalit community. The U.S. statement named the paramilitary Rapid Support Forces, or RSF, which has been locked in a battle with the Sudanese armed forces, as the perpetrator of the ethnic cleansing. The Biden administration had earlier also named the RSF as responsible for genocide.

Declaring an ongoing genocide is one thing. Doing something immediately to alleviate it is more important. The United States and the world must not fail to act.

The State Department’s declaration happened to come on the eve of the anniversary of another mass atrocity. Fifty years ago, on April 17, 1975, the Khmer Rouge seized control of the Cambodian capital, Phnom Penh, and launched a fanatical experiment to remake society through the systematic extermination of professionals, businesspeople, intellectuals and ethnic minorities. Up to 3 million people perished from summary executions, forced labor and starvation in the nearly four years of genocide that ensued. This horror, too, took place amid global indifference.

At the time, the United States was in retreat from Southeast Asia, scarred by its humiliating military failure in Vietnam. A 1976 memo from President Gerald Ford’s national security adviser, Brent Scowcroft, outlined reports of widespread executions of former government officials, soldiers, teachers, students and anyone showing signs of having been educated. But neither Ford nor his successor, President Jimmy Carter, took action to stop the bloodletting or even to raise awareness of it.

Now that the Trump administration has recognized a genocide is occurring in Sudan, what, if anything, can the United States do to end it?

Sudan’s civil war defies any easy solution. The conflict stems from a power struggle between two warring generals who once were allies: Gen. Abdel Fattah al-Burhan, the armed forces commander, and Mohamed Hamdan Dagalo, known as Hemedti, commander of the RSF, which is the contemporary offshoot of the Janjaweed militia that, in the early 2000s, terrorized Darfur and was responsible for Sudan’s first genocide. When the generals’ tenuous alliance snapped two years ago, their artillery and tank battles left much of the capital, Khartoum, in ruins.

In late March, there seemed to be a major break in the stalemate when Burhan’s forces managed to recapture Khartoum. But Hemedti retreated west to his stronghold in the Darfur and Kordofan regions, where he has set up a rival ” Government of Peace and Unity.” And he has formed an alliance with a militia group called the Sudan People’s Liberation Movement-North, a remnant of South Sudan’s independence war. Hemedti’s moves to declare a rump state now risk splintering Sudan. Meanwhile, the massacres of the Masalit people and other non-Arab minority groups continue.

The participants in Sudan’s civil war include a volatile mix of regional and international players, with their own agendas and long-standing rivalries. Burhan is backed by Egypt, as well as Saudi Arabia and Qatar. Iran, hoping to expand its influence to the Red Sea, is also backing the Sudanese armed forces, supplying drones and other weapons. And Turkey has sent drones and missiles. The RSF, for its part, is supported by the United Arab Emirates as well as Libya, Chad, the Central African Republic and South Sudan. Hemedti has also been welcomed in Ethiopia, Uganda and Kenya.

With such a combustible brew, the temptation might be to turn a blind eye. But this would be wrong — just as it was wrong for the United States half a century ago to ignore the atrocities of Cambodia’s killing fields.

Strong action does not have to mean direct intervention. The Trump administration could halt arms sales to the UAE and impose sanctions, until the country ends its military and financial support for Hemedti’s RSF. Other countries that seem to support the RSF should be warned. And the United States should appoint a special envoy to the region to kick-start diplomacy by leaning on Egypt, Saudi Arabia and other U.S. allies to bring their client to the negotiating table.

President Donald Trump wants to be known as a peacemaker. Sudan might not be high on his priority list, but he should nevertheless pay attention. By helping to reach a peace agreement there, he could stop a genocide and end the world’s biggest humanitarian nightmare.