As Manasseh could not have executed Isaiah until after the death of Hezekiah, who Isaiah was closely allied with, Isiah could not have been killed until after 687 BC and must have been killed before 643 BC. It is reported in Rabbinical literature that Isaiah was the maternal grandfather of Manasseh, which, if true, would mean Isaiah was the father of Manasseh’s mother Hephzibah, and thereby father-in-law of King Hezekiah, which would support Isaiah’s claim to have been a major prophet in the time of Hezekiah’s father Ahaz’s reign, between 732 and 716 BC. Therefore his rise to prominence as a prophet must have taken place during the reign of King Jotham, circa 742 and 735 BC, and likely his predecessor king Uzziah between 783 and 742 BC. This indicates that Isaiah was in his 90s or older when Manasseh had him executed, which makes his climbing a tree unlikely and supports the alternate report, that Manasseh had him sawed in half, and not a tree he was hiding in. The book of 4th Kingdoms reports that Manasseh killed supporters of his father Hezekiah’s religious reforms, which would have undoubtedly included Isaiah, and therefore, while the execution of Isaiah is not itself found in the Septuagint or Masoretic Tanakh, it is implied.
Archaeological evidence has shown that at the beginning of the era of Isaiah, the Kingdoms of Samaria and Judah went through considerable changes. When Uzziah reigned in Jerusalem, the larger Kingdom of Samaria to the north was the wealthiest and most populous nation in Canaan and had occupied the kingdoms of Aram and Hama to the north, giving the Samarians a dominant position in the region, occupying most of modern northern Israel, the northern Palestinian West Bank, eastern Lebanon, and western Syria. At the time, the coastal cities of Sidon and Tyre continued to be independent, as well as Judah to the south, and Moab, Ammon, and Edom to the southeast. This era of wealth and prosperity was suddenly and dramatically ended by a magnitude 8 earthquake circa 760 BC, which would have caused aftershocks for up to a year. Entire cities were leveled, and the Dead Sea fault Zone was radically altered, causing a drop in the water levels and a general drying of the Arabah region to the south of the Dead Sea.