Many times, as was the case with Babylon, the people just surrendered because they heard what a great king Cyrus the Great was. Cyrus waited until the Babylonians were thoroughly disgusted with their ruthless king, and then when he marched on the city, the people simply opened the gates. They had heard what a great and merciful king Cyrus was, and they would much rather have him than their current one.
Their empire provided a large revenue.
Roman Empire ruled most of the known land at the time.
Persia's absorption of Media gave it the strength to expand into an empire covering the Middle East, north Africa and central Asia.
The Assyrians were the citizens an ancient empire centered on what is now Iran (Persia).
The Greek city-states in Asia Minor revolted against Persian rule. Cities outside the Persian Empire intervened, so the Persians decided to incorporate them within its empire to enforce peace.
The Persians had been dominated by the Medes, but king Cyrus took over Media and joined their forces together which enabled him to take over the Babylonian Empire. With this even greater power, he was able to expand through Western Asia, and into Central Asia.
The Ancient Persians were captured twice.
They used the same technique as had other empires - conquest.
The Babylonians were a people who established an empire in the Middle East. The Persians were a tribe to the east in today's Iran, who established an empire by defeating Medes and used the combined strength to take over the Babylonian Empire.
Persians.
Gaining an empire is its own reward.
The Persians absorbed the Phoenicians into their empire, and used their resources.