When Alexander, the great Macedonian conqueror, invaded India in 327 B.C., the various kingdoms and republics of the North-West failed to forge a united front against the common enemy. Some rulers, like Ambhi, submitted without resistance, while others, like Paurava and the chief of Massaga, refused to bow to Alexander even when defeat seemed certain. Although Alexander met his match in King Paurava, he managed to overpower him. Alexander was also helped by the weather, the heavy rain on the day before the battle had made the earth wet, so that Paurava's able archers found it difficult to rest their bows on the slippery ground. Nineteen Greek writers, who either accompanied Alexander or visited India soon after the invasion, wrote accounts of Alexander's march. Based on these early records Arrian (1st century A.D.) wrote his biography of the Macedonian conqueror. This and other works by Curtius, Diodoros, Plutarch and Justin describe Alexander's invasion but there is no detailed Indian source to which we can turn. It is, therefore, difficult to trace Alexander's movements in India with precision or to identify the tribes he encountered in the course of his arduous march.