On the fifth day they came to the end of the flat country. They had now to cross a range of hills, and at this they rejoiced, thinking that the hilly ground would be disadvantageous for the Persian cavalry. But this day was destined to be the most disastrous of any they had yet known. Seeing in the distance a palace with several villages clustering round it, they decided to make for it. The road lay over hilly ground, and they had already climbed the first hill when they received an unexpected check. As they descended the farther side, the enemy appeared upon the height they had just left, and discharged a volley of stones and arrows upon the light-armed infantry, killing and wounding many of them. To this the Hellenes replied by sending a detachment of hoplites to march back up the hill, and dislodge the Persians. Their heavy armour protected them to some extent, but made it impossible for them to advance rapidly, and the nimble Persians quickly withdrew beyond their reach, returning however as soon as the hoplites turned back to rejoin their comrades, and discharging their shots and arrows as before. [Illustration: THE HILL COUNTRY EAST OF THE TIGRIS.] At the second hill, the same thing happened again, and now the Persian cavalry were also brought into play, and directed to chase the Hellenes at full speed down the steep descent. This they did, but only when they had been driven to their work with whips. Meanwhile the hail of stones and arrows continued, and made such havoc in the ranks of the light-armed troops who wore neither helmet nor coat of mail, that it became urgently necessary to find some means of diverting the attention of the enemy. Calling a short halt, the generals rapidly took counsel together, and formed a plan by which the light infantry could be placed beyond the reach of danger, and at the same time give assistance to their comrades. Parallel with the range of hills over which the Hellenes were making their way, was a range of mountains, from whence the road along the hills could be overlooked. To these mountains the light-armed troops were despatched, with instructions to keep pace with their comrades on the lower level, and rain down shots and arrows upon the enemy whenever they attempted to hinder them in their march. As soon as the Persians perceived this device, they gave up the pursuit. The disadvantage was now on their side, and they were afraid of being cut off from the main body of their army.