The Achaemenid conquest of the Indus Valley occurred from the 6th to 4th centuries BCE, and saw the Persian Achaemenid Empire take control of regions in the northwestern Indian subcontinent that predominantly comprise the territory of modern-day Pakistan. The first of two main invasions was conducted around 535 BCE by the empire's founder, Cyrus the Great, who annexed the regions west of the Indus River that formed the eastern border of the Achaemenid Empire. Following Cyrus' death, Darius the Great established his dynasty and began to re-conquer former provinces and further expand the empire. Around 518 BCE, Persian armies under Darius crossed the Himalayas into India to initiate a second period of conquest by annexing regions up to the Jhelum River in Punjab.