Titus Livius (Livy), The History of Rome, Book 41
Evan T. Sage, Ph.D. and Alfred C. Schlesinger, Ph.D., Ed.

26. The Celtiberians in Spain, who had surrendered to Tiberius Gracchus¹ after their defeat in the war, had remained quiet while Marcus Titinius² [p. 275]held the province as praetor. They rebelled on the³ arrival of Appius Claudius⁴ and began the war by a surprise attack on the Roman camp. [2] It was about daybreak, when the sentinels were on the rampart and the outposts were on guard at the gates, that they saw the enemy coming afar off and called the troops to arms. [3] Appius Claudius, after displaying the signal for battle and briefly exhorting the troops, led them out by three gates at once. The Celtiberians met them as they came out, and at first there was a drawn battle, since on account of the narrow space not all the Romans could fight in the entrance; [4] then, as they pressed forward one on another, when they had forced their way out beyond the rampart in order that they might extend their line and form it to meet the flanks of the enemy by which they were being surrounded, they burst out so suddenly that the Celtiberians were unable to withstand the charge. [5] Before the second hour they were repulsed; about fifteen thousand were killed or captured, and thirty-two standards were taken. The camp was also captured that day and the war was over: for those who survived the battle scattered to their towns. Thereafter they quietly submitted to authority.