Today, 2060 years ago (according to the old Roman calendar), Caesar crossed the Rubicon and uttered the so famous phrase alea iacta est – the die is cast. But what did really happen that day and how much do we really know about the event? I am by no means an expert on Caesar and the civil wars, but I will attempt to at least present our primary sources.
First of all, it seems as if the nobility had realised for some time that a civil war was to be. It is interesting to read Cicero's own words on the matter:
"I have often told you [M Caelius Rufus] in my letters that I see no chance of peace lasting a year; and the nearer the struggle comes, which must come, the clearer does that danger appear. The point, on which the men in power are bound to fight, is this - Cn. Pompeius has made up his mind not to allow C. Caesar to become consul, except on condition of his first handing over his army and provinces: while Caesar is fully persuaded that he cannot be safe if he quits his army."
Cicero - Letters CCLXXIX
Translated by E. S. Shuckburgh 1908-1909
The first person to describe the event was Caesar himself. He is, however, clearly aware of the fact hat to cross the river is to break the law and much more attention is given to explaining his motifs and reasons behind the act than to describe the event itself.
“What could all this [the actions of Caesars enemies] aim at but his destruction? That, nevertheless, he was ready to agree to any proposal, and expose himself to any danger, for the sake of his country.”
Caesar - Commentarii de Bello Civili I.9
Translated by W. Duncan 1856
He even mentions how the soldiers were enraged by the behaviour of the senate:
“The soldiers of the thirteenth legion, who were present, and whom he had sent for in the beginning of the troubles, (the rest not being yet arrived,) cried out, that they were determined to maintain the honour of their general, and to revenge the wrongs done to the tribunes.”
Caesar - Commentarii de Bello Civili I.7
Translated by W. Duncan 1856
The crossing itself was, however, all but omitted - it is quite possible that Caesar had no intention of drawing attention to it:
“He [Caesar] [...] sent Antony to Arretium [on the other side of the Rubicon], with five cohorts; remained himself at Rimini, with two, where he resolved to levy troops; and seizing Pisaurum, Fanum, and Ancona, left a cohort in each for a garrison.”
Caesar - Commentarii de Bello Civili I.11
Translated by W. Duncan 1856
Later authors were, on the other hand, very interested in the event and it soon became myth. It is unfortunate that Livy's 105th book is lost and we must turn to a somewhat later source for our next accound; Plutarchos' Parallel Lives.
“He [Caesar] himself spent the day in public, attending and watching the exercises of gladiators; but a little before evening he bathed and dressed and went into the banqueting hall. Here he held brief converse with those who had been invited to supper, and just as it was getting dark and went away, after addressing courteously most of his guests and bidding them await his return. To a few of his friends, however, he had previously given directions to follow him, not all by the same route, but some by one way and some by another. He himself mounted one of his hired carts and drove at first along another road, then turned towards Ariminum. When he came to the river which separates Cisalpine Gaul from the rest of Italy (it is called the Rubicon), and began to reflect, now that he drew nearer to the fearful step and was agitated by the magnitude of his ventures, he checked his speed. Then, halting in his course, he communed with himself a long time in silence as his resolution wavered back and forth, and his purpose then suffered change after change. For a long time, too, he discussed his perplexities with his friends who were present, among whom was Asinius Pollio, estimating the great evils for all mankind which would follow their passage of the river, and the wide fame of it which they would leave to posterity. But finally, with a sort of passion, as if abandoning calculation and casting himself upon the future, and uttering the phrase with which men usually prelude their plunge into desperate and daring fortunes, "Let the die be cast," he hastened to cross the river; and going at full speed now for the rest of the time, before daybreak he dashed into Ariminum and took possession of it.”
Plutarchos - Βίοι Παράλληλο (Parallel lives) Caesar XXXII. 4-8
Translated by B. Perrin
You can clearly see how Plutarchos either had better sources than Caesar himself, wanted to portray it in a different manner or embellished the story.
Suetonius, another very famous Roman author, publish another version of the event around 120 AD, some 50 years later than Plutarchos.
"[...] when word came that the veto of the tribunes had been set aside and they themselves had left the city, he at once sent on a few cohorts with all secrecy, and then, to disarm suspicion, concealed his purpose by appearing at a public show inspecting the plans of a gladiatorial school which he intended building, and joining as usual in a banquet with a large company. It was not until after sunset that he set out very privily with a small company, taking the mules from a bakeshop hard by and harnessing them to a carriage; and when his lights went out and he lost his way, he was astray for some time, but at last found a guide at dawn and got back to the road on foot by narrow by-paths. Then, overtaking his cohorts at the river Rubicon, which was the boundary of his province, he paused for a while, and realising what a step he was taking, he turned to those about him and said: "Even yet we may draw back; but once cross yon little bridge, and the whole issue is with the sword."
As he stood in doubt, this sign was given him. On a sudden there appeared hard by a being of wondrous stature and beauty, who sat and played upon a reed; and when not only the shepherds flocked to hear him, but many of the soldiers left their posts, and among them some of the trumpeters, the apparition snatched a trumpet from one of them, rushed to the river, and sounding the war-note with mighty blast, strode to the opposite bank. Then Caesar cried: "Take we the course which the signs of the gods and the false dealing of our foes point out. The die is cast," said he."
Suetonius - Divus Julius 31-32
Translated by J.C. Rolfe
Appian, however, turns down some of the mythical content in his version, which was written in the middle of the 2nd century AD, another 30 years or so after Suetonius.
"Toward evening Caesar himself rose from a banquet on a plea of indisposition, leaving his friends who were still feasting. He mounted his chariot and drove toward Ariminum, his cavalry following at a short distance. When his course brought him to the river Rubicon, which forms the boundary line of Italy, he stopped and, while gazing at the stream, revolved in his mind the evils that would result, should he cross the river in arms. Recovering himself, he said to those who were present, "My friends, to leave this stream uncrossed will breed manifold distress for me; to cross it, for all mankind." Thereupon, he crossed with a rush like one inspired, uttering the familiar phrase, "The die is cast: so let it be!" Then he resumed his hasty journey and took possession of Ariminum about daybreak"
Appian - Bella Civilia XXXV
Translated by H. White 1912-1913
It is interesting that we find the same pattern in Dio Cassius histories, which were written roughly between 201 and 223 AD. The crossing has now changed again, from a mystical event to one out of many important affairs that had to be recorded.
"When Caesar was informed of this, he came to Ariminum, then for the first time overstepping the confines of his own province, and after assembling his soldiers he ordered Curio and the others who had come with him to relate to them what had been done."
Cassius Dio - Roman History XLI. 4
Translated by E. Cary 1914-1927