What was the reason for Abu Bakr Al-Siddiq, may Allah be pleased with him, waging war on the Persian Empire?

The most important battles for the conquest of Persia took place during the era of Umar ibn al-Khattab, may Allah be pleased with him, such as al-Qadisiyyah and Nahavand. However, the conquest of Iraq, which was under Persian control, began during the era of Abu Bakr al-Siddiq, may Allah be pleased with him. Al-Siddiq sent Khalid ibn al-Walid and al-Muthanna ibn Harithah to conquer Iraq. The goal of these conquests was to convey the message of Islam to people and to subdue the powers that prevented them from hearing the truth. If they did not embrace Islam, they would pay jizya, which allowed them to learn about Islam and might encourage them to embrace it voluntarily. This is what happened in most of the countries conquered by Muslims.