WASHINGTON — Early this month, the Ethiopian government declared that it was finally ready to implement a peace deal it signed with Eritrea nearly two decades ago. The Eritrean government didn’t respond to the announcement for over two weeks — until Wednesday, when President Isaias Afwerki said that “the positive direction that has been set in motion is crystal clear.” Mr. Isaias also promised to send a delegation to Ethiopia “to gauge current developments directly and in depth.”

For many years, however, even as Ethiopia declared its willingness to implement a 2002 judgment about the two states’ border, it refused to withdraw its troops from Eritrean territory until other issues — about armed groups, trade, access to Eritrea’s ports on the Red Sea — were settled. But Eritrea refused to negotiate at gunpoint, especially over a boundary decision that both governments had committed to uphold whatever its outcome.

So why the surprise breakthrough now?

Analysts have pointed to two factors: the advent of Ethiopia’s new prime minister, Abiy Ahmed, who in just a few months has embarked on a series of ambitious domestic reforms, and a recent trip to Eritrea by Donald Yamamoto, the acting head of the State Department’s Africa bureau, a rare visit for a senior American diplomat. A changing of the guard in both countries appears to explain this watershed moment.

Image Prime Minister Abiy Ahmed of Ethiopia on Thursday. Credit... Yonas Tadesse/Agence France-Presse — Getty Images

Except that it doesn’t. Ethiopia’s policy toward Eritrea was shifting well before Mr. Abiy came to power, largely as a result of fundamental domestic factors. And America’s policy in the Horn of Africa hardly has changed: It is as misguided as ever, with its overriding focus on counterterrorism. What’s more, the United States has far less sway over Ethiopia than it would like or than is often assumed.