Bangladesh, Feb. 24 -- When a nation seals its border, it is rarely just a security decision. It is a declaration of vulnerability, a signal of exhaustion, and sometimes a warning to the world. Chads decision to close its eastern frontier with Sudan is all three.

The announcement from NDjamena follows deadly clashes near the border town of Tiné, where violence linked to Sudans civil war spilled across an already fragile boundary. Five Chadian soldiers and three civilians reportedly lost their lives. For a country that has tried to walk a careful diplomatic line between Sudans warring factions, the deaths represent more than a security breach-they represent the tangible cost of a conflict that refuses to remain confined within Sudans...