Scandinavia fed off of trade with the Celts (450–50 B.C.) importing improved cart, ship, and metalworking technology. Contact with Rome (c. 50 B.C.–A.D. 400) enriched the upper classes with fine silver, ceramics, and glass. More ominously, Scandinavians returning from Roman military service brought back advanced weapons and armor. Petty kings surrounded by loyal bands of warriors emerged, along with the first Scandinavian sailing ships that would soon take them abroad.