In appallingly rugged country his road ran through a narrow defile, perhaps the modern Shipka pass, whose tribesmen had bivouacked behind a defending line of carts. First, as in Thessaly, Alexander looked for a way round them; he failed, so he assessed the chances of forcing them directly. The carts seemed a defence, but he quickly realized they could also be rolled downhill into his packed ranks; his men were told to advance, and those with room to manoeuvre were ordered to spread out if the carts began rolling, those with proper shields were to lie flat on the ground and use them as cover. Down came the carts, and some ranks opened, others dropped down as ordered, and the carts either rumbled through the gaps or else bounced over the wall of shields, 'and not one of the Macedonians was killed', implied Alexander's friend Ptolemy* in his history of the incident. When Alexander faced Persian chariots four years later, he defeated them as he defeated these Thracian carts; great generals remember ruses which have worked before, and soon he would show that he memorized as much from reading as from experience.
Thrace's wooded landscape was more of an obstacle than its unarmoured tribesmen, so much so that Philip had once used a pack of hounds to flush his enemy from the thickets. Alexander balanced his weapons nicely. His father's slingers and archers provoked the barbarians out of the woods, then his infantry pitched into them, uphill if necessary, and his cavalry either jostled or punched in from the flanks wherever there were clearings. Before long he had routed the Triballians so thoroughly that their king retreated with a few loyalists to an island in the Danube itself, where he was watched from the far bank by its nomadic tribesmen.
* I do not, of course, imply that Ptolemy's entire history or precise words have ever survived; sec the General Note on Sources at the end of this book for this point and for the identity of our main historians.
Alexander despatched his booty back to Macedonia, for he remembered his father's unhappy losses, and advanced to Europe's great river to round off his first foreign campaign.
His ships met him as requested, but they were too few and feeble to storm the Triballian island, so Alexander abandoned the sea power which, like Napoleon, he never mastered, and decided to float his troops across the Danube for a show of terror on the far bank. Fishing canoes were commandeered, and orders were given for the troops to fill their leather tent-skins with chaff and sew them together to make rafts; on these makeshift transports they crossed the river under cover of night, their horses swimming beside them. They landed cunningly near the cover of a tall cornfield, and were led through the crops by the Foot Companions who smoothed a way with the flat blades of their sarissas. On open ground, they loosed a classic charge, punching forwards with the Companions on the right wing, backing up with sarissas in square formation in the centre. The tribesmen fled first to a fort, then retreated on horseback into the steppes. Alexander knew better than to follow a retreating enemy into barren steppeland, and so returned to count the plunder and sacrifice to 'Zeus the Saviour, Heracles and the river Danube for allowing him to cross it'.
The manner of his crossing was not just a matter of the river's goodwill. Nomad relations of the Danube tribesmen were known to stuff their horses' skins with chaff when they died, but there is no evidence that Alexander's straw-stuffed rafts were a native custom; they belonged, rather, to the East, to the Euphrates and the Oxus, and the rivers of the Punjab where stuffed skins able to carry some two hundred pounds still serve as kilikrafts for the natives. No Macedonian had ever seen so far into Asia, and only one Greek general had described it; Xenophon the Athenian, who led the Ten Thousand Greeks through Mesopotamia at the turn of the century, and recorded his march in his memoirs. Faced with the Euphrates he had been shown how to cross it on rafts of stuffed skins; at the Danube, Alexander evidently turned to a trick he had read in a military history.
After the bold example of the first Balkan troops ever to cross the Danube, tribes along the river sent presents of friendship, and the Triballians surrendered on their island; later, more than 2,000 joined Alexander in Asia. Even the so-called Celts of western Europe who lived far up river near the Adriatic coast, sent envoys to plead for alliance. Alexander asked them, wrote his friend Ptolemy, 'what they feared most in the world, hoping they would say himself, but they replied that they were most afraid that the sky would fall on to their heads', an old Celtic belief which had already been described by Herodotus; not for the last time, a Macedonian described an unknown tribe through Herodotean eyes. But the Celts' presence was more pleasing than their stubbornness, for Macedonia was serving history in a way that her Greek subjects could not recognize at the time; bestriding the Balkans, she acted as a barrier against the pressure of Europe's restless tribesmen, and a strong Macedonia guaranteed the safety of the Greeks' city life in the south. Not for another fifty years would hordes of Gauls pour into Greece from Europe and threaten her civilization, and then only at a time of feeble confusion in the Macedonian royal family. The European conquests of Philip and Alexander belonged to a wider perspective, essential to the safety, if not the freedom, of Greece. But there was another corridor to Europe, and no sooner had Alexander received the Celts than he heard that it too was giving trouble.
West and north-west of Macedonia's highlands lived the tribes of Illyrians whose villages controlled the main road of invaders from Europe into Greece and whose kings were dangerous in their own right. When Philip took the kingdom, they had overrun much of Macedonia, killing the king and claiming heavy tribute. Philip fought them back, and pierced far up the Adriatic Coast at all seasons to harass them; he had peopled his north-west frontier with new garrison towns, uprooting his subjects 'like a shepherd who moves his flocks from winter to summer pastures', but he had never ensured their security and the Illyrians had been one of the failures of his reign. The king he had learnt to respect was Bardylis, who had twice exacted tribute from Macedonia and was known as an extraordinarily rich man; he had recently died aged ninety, and it was his son who threatened Alexander with frontier war.
Within weeks, the Danube had been forgotten and Alexander was deep in Illyrian marshes and borderlands. Penning Bardylis's son into a stronghold in late summer he had settled down to besiege him in a narrow glen, only to find that a neighbouring king appeared in force along the passes that blocked his escape. This was a very unpleasant situation. He was short of food and his foraging-parties had to be rescued from harassment; he could not retreat unchallenged, for Bardylis's son would sortie from his fort and launch into his rear with troops who had already shown proof of their taste for human sacrifices. The escape route was a narrow wooded valley between the foot of a sheer mountain and a river beneath, and it was only broad enough for four men abreast. Trapped, Alexander resorted to an impudent bluff.
On his patch of open ground, he narrowed his infantry into a line 120 ranks deep and placed a few cavalry on either wing. Sarissas were to be held erect and on command, the first five ranks were to lower them for the charge and swish them in perfect time from left to right; all troops would advance, swinging from one wing to the other to match the front sarissa bearers, and they would form into a wedge on the left and charge towards the enemy. Shields were to be clashed and the war-cry of Alalalalaiwas to be echoed down the glen. On the first rapid strides forward, the main enemy fled in panic from the hill-tops, scared by the disciplined drill and the sound of the war-cry.