Titus Livius (Livy), The History of Rome, Book 31
Evan T. Sage, Ph.D. Professor of Latin and Head of the Department of Classics in the University of Pittsburgh, Ed.

39. The consul was engaged in refreshing himself at the time it was announced that the herald had come and why he had come. [2] Replying merely that in the morning there would be opportunity for a conference, he gave Philip what he sought, the chance to retire rapidly during the night and a part of the next day. [3] He made for the mountains, choosing a road which he knew the Roman, with his heavy-armed column, would not take. At daybreak the consul sent the herald away after granting the truce, and when he learned, no long time later, that the enemy had gone, not knowing where to pursue him, he spent some days in the same camp while gathering supplies. [4] Thence he marched to Stuberra and [p. 115]brought there from Pelagonia the grain which was in¹ the fields. He then marched to Pluinna, still ignorant as to where the enemy had gone. [5] When Philip had established a base near Bruanium, marching from there across country he inspired sudden terror in the enemy. On that account the Romans moved from Pluinna and encamped on the Osphagus river. [6] The king also pitched camp not far away, throwing up a rampart along the bank of a river —the natives call it Erigonus. [7] Then, feeling certain that the Romans would move toward Eordaea, he hurried forward to gain the pass, that the Romans might not force the road, which was closed by the narrow entrance. [8] There he threw up hasty fortifications, using sometimes a rampart, sometimes a ditch, sometimes piles of stones to serve as a wall, sometimes cut-down trees, as the nature of the terrain [9] and the material at hand permitted, and, as he thought, rendered a road which was already naturally difficult impassable by the obstacles which he placed in all the open places. [10] There were many forests in the neighbourhood, a great hindrance to the Macedonian phalanx,² which was of absolutely no use except where it could thrust, so to speak, a rampart in front of the shields with its very long spears, and for this purpose they needed open country. [11] The Thracians too were impeded by their lances, which were likewise of great length, among the branches which projected in every direction. [12] Only the Cretan contingent was of much service, but even they, since they could only, if there was an attack, direct their arrows against unprotected horses and riders, so against the Roman shields they lacked the power of penetration, and there were left no unexposed parts at which they could aim. [13] [p. 117]And so, when they perceived that weapons of this³ kind were ineffective, they harassed the enemy with the stones which lay everywhere through the whole valley. The clash of these against the shields, causing more noise than damage, delayed the advancing Romans for a little while. [14] Then, scorning these also, part of the Romans, forming a testudo,⁴ advanced in face of the enemy, while others, gaining the saddle by a short detour, [15] dislodged the terrified Macedonians from their strong points and outposts, and even killed some of them, since flight was slow in the difficult country.