What did Alexander the Great achieve that significantly expanded his territory?

Alexander the Great is renowned for his military prowess and ambition, which culminated in the significant expansion of his empire through the defeat of the Persians. This monumental achievement allowed him to gain control over a vast territory that previously belonged to the Persian Empire, which included parts of Asia Minor, Syria, Egypt, and into the heart of Persia itself.

Defeating the Persians not only showcased his tactical genius but also facilitated the spread of Greek culture and influence across the regions he conquered. This expansion led to the establishment of cities, most notably Alexandria in Egypt, and integrated various peoples into his empire, creating a legacy that blended cultures.

While unifying Greece was an important step in Alexander's rise, it was his campaigns against the Persians that directly resulted in territorial expansion, making this achievement a cornerstone of his historical significance. The other options, such as conquering Rome and invading Egypt, reflect important events in his life but do not compare to the impact of his victories over Persia in terms of territory gained and historical consequence.