When Darius had become King, he determined, like the Great Kings before him, to add yet more lands to his empire, and so made ready an army which was to invade Scythia, the region north of the Black Sea. As the Persians themselves were not naturally sailors, the Greeks in the Ionian cities were forced to send a large number of ships to the help of this expedition.
Darius and his army set out, and, arriving at the River Ister (now known as the Danube), were joined by the Ionian ships. Here Darius commanded that a bridge of boats should be built, and then taking a cord in which he tied sixty knots, he called the Ionian leaders together and said to them:
Men of Ionia, do ye now keep this rope and do as I shall say:—So soon as ye shall have seen me go forward against the Scythians, from that time begin, and untie a knot on each day: and if within this time I am not here, and ye find that the days marked by the knots have passed by, then sail away to your own lands. Till then, guard the floating bridge, showing all diligence to keep it safe and to guard it. And thus acting, ye will do for me a very acceptable service.
Having said this Darius hastened forward on his march.
Scythia was a land totally unknown to the Persians, and strange tales were told in after years of the adventures of the King and his army. The Scythians were a nomad people, and they believed themselves to be invincible. When they heard that Darius was in their land with the intention of conquering it, they "planned not to fight a pitched battle openly, but to retire before the Persians and to drive away their cattle from before them, choking up with earth the wells and the springs of water by which they passed and destroying the grass from off the ground." For some time Darius pursued this mysterious people, but he could never come up with them.
Now as this went on for a long time and did not cease, Darius sent a horseman to the King of the Scythians and said as follows: "Thou most wondrous man, why dost thou fly for ever, when thou mightest do of these two things one?—if thou thinkest thyself able to make opposition to my power, stand thou still and cease from wandering abroad, and fight; but if thou dost acknowledge thyself too weak, cease then in that case also from thy course, and come to speech with thy master, bringing to him gifts of earth and of water." To this the King of the Scythians made reply: "My case, O Persian, stands thus: Never yet did I fly because I was afraid, either before this time from any other man, or now from thee; nor have I done anything different now from that which I was wont to do also in time of peace: and as to the cause why I do not fight with thee at once, this also I will declare unto thee. We have neither cities nor land sown with crops, about which we should fear lest they be captured or laid waste, and so join battle more speedily with you; but know this that we have sepulchres in which our fathers are buried; therefore come now, find out these and attempt to destroy them, and ye shall know then whether we shall fight with you for the sepulchres or whether we shall not fight. Before that, however, we shall not join battle with thee. About fighting let so much as has been said suffice; but as to masters, I acknowledge none over me but Zeus my ancestor and Hestia the Queen of the Scythians. To thee then in place of gifts of earth and water I shall send such things as it is fitting that thou shouldest receive; and in return for thy saying that thou art my master, for that I say, woe betide thee."
The King of Scythia sent gifts to Darius as he had promised, strange and mysterious gifts. He sent him a bird, a mouse, a frog and five arrows. At first the Persian could not imagine what these gifts might mean, but one of his wise men interpreted them as meaning that "unless ye become birds and fly up to the heaven, or become mice and sink down under the earth, or become frogs and leap into the lakes, ye shall not return back home, but shall be smitten by these arrows."
The Scythians continued to lead the Persians from place to place in this strange campaign, until at last they brought them back again to the Ister where the Ionians were guarding the bridge of boats. The Scythians arrived first, and they tried to persuade the Ionians to break up the bridge, so that Darius would find no means of escape and would then fall into their hands. Some of the Greeks were in favour of doing this, but the Tyrant of Miletus, who wanted to keep on good terms with Darius, advised against such treachery and his word prevailed. In order to get the Scythians away, they pretended, by moving a few of the boats,, that they were going to destroy the bridge, but when Darius came, after a moment's fear that he had been deserted, he found the bridge still there, and he crossed safely and returned to his own land.
When Darius learned that it was owing to the advice of the Tyrant of Miletus that the bridge had been saved, he sent for him and praised him highly for what he had done, telling him he knew him to be a man of understanding and well-disposed towards him, and that in consequence he wished him to go with him to Susa, to eat at his table and to be his counsellor. Darius did this because in reality he distrusted him and preferred that he should be near him in Susa, where his movements could be watched.