Short answers, pulled from the story.
Assyria existed as a city-state from the 21st century BC and as an empire from the 14th century BC until 609 BC. Historians divide its history into the Early Assyrian period around 2600-2025 BC, the Old Assyrian period around 2025-1364 BC, the Middle Assyrian period around 1363-912 BC, the Neo-Assyrian period from 911-609 BC, and a post-imperial period extending to around 240 AD.
The Neo-Assyrian Empire reached its greatest extent under Esarhaddon, who conquered Egypt in 671 BC. At its peak the empire stretched from parts of modern-day Iran in the east to Egypt in the west, making it the largest empire yet assembled in world history at that time.
The Neo-Assyrian Empire collapsed after the death of Ashurbanipal in 631 BC, largely because of the persistent "Babylonian problem": revolts in Babylonia were frequent throughout the Sargonid period despite repeated attempts at appeasement. The revolt of Babylon under Nabopolassar in 626 BC, combined with a Median invasion under Cyaxares beginning in 615-614 BC, produced the Medo-Babylonian coalition that sacked Assur in 614 BC and Nineveh in 612 BC. The last Assyrian ruler Ashur-uballit II was defeated at Harran in 609 BC.
Under Erishum I, who ruled around 1974-1934 BC, Assur conducted what historians consider the earliest known experiment in free trade in world history. The initiative for trade and large-scale foreign transactions was left entirely to the populace rather than the state. The network that resulted transported around one hundred tons of tin and 100,000 textiles to Anatolia, while roughly twenty-five tons of Anatolian silver came back to Assur in the period around 1950-1836 BC.
Per estimates by scholar Karen Radner, an official message sent from the western border province of Quwe to the Assyrian heartland, a distance of 700 kilometers across terrain with no bridges over its rivers, could arrive in under five days. That communication speed was not surpassed in the Middle East until the Ottoman Empire introduced the telegraph in 1865, nearly two and a half thousand years after the Neo-Assyrian Empire's fall.
Assyrian culture and population continued in the former heartland through successive empires including the Achaemenid, Seleucid, Parthian, and Sasanian. The Assyrian people were gradually Christianized from the 1st century AD onward. The Sayfo, the Assyrian genocide enacted in the late 19th and early 20th centuries, killed as many as 250,000 Assyrians. Further massacres and persecutions have since driven most Assyrians into diaspora, though modern scholars accept on the basis of historical and genetic evidence that the modern Assyrian people are descendants of the ancient empire's population.