Ancient authors on the issue of the Varus Battle

Lucius Annaeus Florus,
Epitome [of Roman History]... 2,30,21-39

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21. I wish he had not thought it of so much importance to conquer Germany. The dishonour with which it was lost was greater than the glory with which it was gained.  
22. But because he knew that Caesar, his father, had twice made bridges over the Rhine to prosecute the war against the country, he was desirous, in honour of him, to make it a province, and it would have been made so effectually, if the barbarians could have endured our vices as well as our government. 
23. Drusus, being sent to the country, first subdued the Usipetes, and then overran the districts of the Tenctheri and Catti. Of the remarkable spoils of the Marcomanni he raised a high mound, by way of a trophy. 
24. Next he attacked, at the same time, the three powerful tribes of the Cherusci, Suevi, and Sicambri, who had commenced the war by burning twenty of our centurions, regarding this proceeding as a bond of union, and entertaining such confident hopes of victory, that they divided the spoil by agreement beforehand.

25. The Cherusci chose the horses, the Suevi the gold and silver, and the Sicambri the captives. But all happened contrary to their expectations; for Drusus, proving conqueror, divided their horses, cattle, gold chains, and themselves, as spoil, and sold them. 
26. For the defence of the provinces, too, he fixed garrisons, and bodies of guards, along the Meuse, the Elbe, and the Weser. On the banks of the Rhine he raised more than fifty fortresses. He built bridges at Bonn and Gesoriacum, and secured them with ships.  
27. He opened a way through the Hercynian forest, which, till that time, had been unpenetrated and unattempted. At length such peace was made throughout Germany, that the inhabitants seemed changed, the ground different from what it was, and the air milder and softer than it was wont to be.  
28. And when that brave young man died there, the senate gave him a surname from the province, (an honour which they had never bestowed on any other general,) not from flattery, but in testimony of his merit. 
29. But it is more difficult to retain provinces than to acquire them. They are obtained by force, but secured by justice.  
30. Our exultation was accordingly but short. The Germans had been defeated rather than subdued. Under the rule of Drusus they respected our manners rather than our arms. But when Drusus was dead, they began to detest the licentiousness and pride, no less than the cruelty, of Quintilius Varus.  
31. He ventured to call an assembly, and administered justice in his camp, as if he could restrain the violence of barbarians by the rods of a lictor and voice of a crier.  
32. But the Germans, who had long regretted that their swords were covered with rust, and their horses idle, proceeded, as soon as they saw the toga, and felt laws more cruel than arms, to go to war under the conduct of Arminius,  
33. while Varus, meantime, was so well assured of peace, that he was not the least alarmed, even by a revious notice, and subsequent discover of the plot, made by Segestes, one of the enemy's chieftains.
34. Having, therefore, risen upon him unawares, and fearing nothing of the kind, while he, with a strange want of precaution, was actually summoning them to his tribunal, they assailed him on every side, seized his camp, and cut off three legions. 
35. Varus met his overthrow with the same fortune and spirit with which Paulus met the day of Cannae.  

36. Never was slaughter more bloody than that which was made of the Romans among the marshes and woods; never were insults more intolerable than those of the barbarians, especially such as they inflicted on the pleaders of causes. 
37. Of some they tore out the eyes, of others they cut off the hands. Of one the mouth was sewed up, after his tongue had been cut out, which one of the savages holding in his hand, cried, "At last, viper, cease to hiss." 
38. The body of the consul himself, which the affection of the soldiers had buried, was dug out of the ground. To this day the barbarians keep possession of the standards and two eagles, the third, the standard-bearer, before it fell into the hands of the enemy, wrenched off, and keeping it hid within the folds of his belt, concealed himself in the blood-stained marsh. 
39. In consequence of this massacre, it happened that the empire, which had not stopped on the shore of the Ocean, found its course checked on the banks of the Rhine.

This webpage reproduces a section of:
Sallust, Florus, and Velleius Paterculus, literally translated, with copious notes and a general index, by the Rev. John Selby Watson, M.A., head master of the Proprietory Grammar School, Stockwell, London: George Bell & Sons, 1889