As Michael Wood stood on the bridge over the river at Issus, his view was obstructed by power lines and superhighways. It was hard to imagine the intensity of that now-famous battle in such ordinary surroundings.

When the two armies met here in November 333 B.C., Alexander and his army were on a mission of revenge. The atrocities of the Persian invasion of Greece 150 years earlier were fresh in their minds and they were determined to exact retribution. While Issus has changed greatly since that day, at the ancient town of Gordion the mood of Alexander's time was almost palpable. The town takes its name from the Macedonian Gordius, who was believed to have settled here, arriving in a wooden cart. As thanks for a journey well-ended, Gordius left his cart at the temple of Zeus. The ordinary cart had an intricate leather knot and pin holding the yoke to its shaft. Local legend had it that the person who could unravel this knot would rule all of Asia. Whether Alexander patiently worked the knot out, or hacked it apart with his sword, we do not know. But the knot was undone and the legend fulfilled. A thunder storm at Alexander's encampment that night confirmed this. Zeus approved.

One wonders what makes this area in northern Iraq one of history's major fault lines -- places marked over and over again by historic eruptions that literally change the course of time -- places where two immutable forces come together, forcing one to give only after the greatest of struggles. The Persian army had massed near Babylon. If Darius had stayed here, Alexander would have been drawn southward into a battle site of Darius' own choosing. Instead the Persian leader pushed his troops 320 kilometers northward to meet the advancing Alexandrian army in the small town of Gaugamela, on one of the most active fault lines in history.

Alexander had now set a determined pace that would bring his army straight into heart of the Persian empire, the city of Persepolis. While one of Alexander's generals lead his troops on a southerly loop through Shirazz, Alexander and 20,000 elite soldiers took a short cut through a narrow path in the Zagros Mountains known as the Persian Gates.

Alexander was deep into the pass before he realized he had fallen into a trap. The Persians had built a wall at the narrowest part of the gap and were waiting for him. Stones, javelins, and artillery rained down on the unsuspecting troops. Leaving their dead behind, Alexander's men withdrew.

There had to be another way, but Alexander interrogated prisoners to no avail. Finally, a local shepherd came forward. There might be a way, he offered; a narrow and difficult path around the back of the pass. Could an army pass through there, Alexander asked. Absolutely not, the shepherd replied. Alexander ordered his men forward on that very route.

Against all odds, Alexander's army crossed the secret and treacherous trail at night and closed his own trap on the Persians. Exactly where was this path? Our local guides debated this well into the night. But, morning found us on the path one of them first thought impossible. Alexander came here in January, he said. The snows would be too deep. Yet this had to be the only way.

Alexander made an encampment here in the foothills of the Hindu Kush. The Russians did as well, establishing their main base here during the Afghan war. It was also the site of one of the greatest archeological finds of this century. Here, diggers uncovered the remains of a great city whose cultural roots were in Greece. The treasures in its storehouses there were incredible: Alexandrian glass, Chinese lacquer, Hindu ivory sculptures -- all testament to the cultural exchanges brought about by Alexander's campaign.