A collection of 1,100 inscribed clay tablets, containing letters to the last rulers of an ancient city destroyed in 1726 B.C., has been discovered in northeastern Syria by a Yale University archeological project.

The tablets are from the royal archive of Shubat Enlil, one of three great, lost capitals of the Near East. They had been sought by archeologists since word of their existence came to light on clay tablets discovered in 1933 at the ancient Syrian city of Mari.

The royal archive was unearthed last fall in an enormous palace being excavated at Tell Leilan by a team led by Harvey Weiss, an associate professor of Near Eastern archeology. By deciphering the cuneiform inscriptions, Weiss and his colleagues hope to read the history of the final days of Shubat Enlil, which was the capital of a powerful but little-known northern Mesopotamian kingdom stretching from the Euphrates River to the Iranian frontier.

Some of the tablets already deciphered contain one of the earliest descriptions of a monarch's use of a cavalry to police the countryside. Weiss said some are letters from neighboring rulers to the king of Shubat Enlil suggesting the kingdoms exchange captured spies. Others, revealing Shubat Enlil's diplomatic relations, show the declining power of Babylon to the south and the growing influence of the western Syrian kingdom of Aleppo.

Weiss said that all of the correspondence dates from about 1740 to 1726 B.C., the period just before Shubat Enlil was destroyed by Samsu-Iluna of Babylon, successor of the famous Babylonian king Hammurabi. But other artifacts found in the palace suggest that still-unexcavated chambers may contain tablets from the reign of the Assyrian king Shamshi-Adad, who ruled Shubat Enlil from 1813 to 1781 B.C., during its heyday.

Weiss said he first surveyed Tell Leilan in 1979 -- a tell is a mound that contains the remains of ancient cities. In 1985, Weiss and colleagues began excavating one room of the palace and discovered 13 tablets whose inscriptions proved that Tell Leilan was the ruins of one of the lost cities. He said other artifacts from the site date from as early as 5000 B.C., and fragments of city walls and buildings show it had become an urban center by about 2600 B.C.

The discovery was reported last week in New York at the annual meeting of the Archeological Institute of America.