NEW YORK — The impassioned chants coming from the multitudes at Tahrir Square — “Leave! Leave!” — will long reverberate in the Arab world and beyond, along with the heart-rending images that kept the world riveted to the tumultuous end of the Hosni Mubarak era in Egypt.

Popular uprisings, often at the crux of great upheavals in the life of a nation, tend to create unforeseen heroes — in Cairo, the affluent young techs who engineered, organized and rallied hundreds of thousands of protesters against the government.

Peaceful pro-democracy movements like theirs also offer a platform to Western nations, especially the United States, to speak loud and clear for the oppressed and against despotic rule, even the rule of a longtime ally.

Cairo’s revolution handed the Obama administration a historic opportunity to act as a moral force in the Arab world. It was an opportunity for President Barack Obama and his chief diplomat, Secretary of State Hillary Rodham Clinton, to speak with one voice and present a clearly defined position.