DANGER ZONES: All Quiet on the Evros

A world which was once set afire by a spark in what is now Yugoslavia has learned to take seriously even the slightest rise in temperature in the Balkan tinder box. Last week diplomatic pulses in half a dozen world capitals thumped over a frontier fracas on a half-submerged sandbank in the unnavigable Evros River which, in one ten-mile stretch, forms the border between Soviet-dominated Bulgaria and U.S.-protected Greece.

All summer long, Greek and Bulgar soldiers had lurked along the Evros, taking potshots at one another. The most serious skirmishes occurred on three swampy sandbanks named Alpha, Beta and Gamma...