contrast to the "accession" method previously in use, whereby the first partial year was counted as year "zero", and "year one" was assigned to the first full year of reign. Thiele attributed this change to the rapprochement between Judah and Israel, whereby Jehoshaphat, Jehoram's father, united with Ahab at the battle of Ramoth-Gilead, and chose a daughter for his son from the house of Ahab (, ). This convention was followed in Judah for the next three monarchs: Ahaziah, Athaliah, and Jehoash, returning to Judah's original accession reckoning in the time of Amaziah. These changes can be inferred by comparison of the textual data in the Bible; however, the biblical texts do not explicitly state whether the reckoning was by accession or non-accession counting, nor do they indicate explicitly when a change was made in the method. Thiele's reckoning has been criticized as arbitrary in its assignment of accession and non-accession dating systems. The official records of Tiglath-Pileser III show that he switched (arbitrarily) to non-accession reckoning for his reign, in contrast with the accession method used for previous kings of Assyria. Tiglath-Pileser left no record for modern historians to indicate which dating method he used, nor whether he was switching from the method used by his predecessors; this is instead determined by comparison of the relevant texts by Assyriologists, the same as Thiele did for the regnal data of Judah and Israel. Co-regency Additional potential confusion arises from periods of co-regency when a son's reign may begin prior to the end of his father's reign. In those situations, years of reign are specified in terms of both the father and of the son. At times, the period of co-regency is clearly indicated, while in others it must be inferred from the source material. As an example of the reasoning that finds inconsistencies in calculations when coregencies are a priori ruled out, dates the fall of Samaria (the Northern Kingdom) to the 6th year of Hezekiah's reign. William F. Albright dated the fall of the Kingdom of Israel to 721 BC, whereas E. R. Thiele calculated the date as 723 BC. If Albright's or Thiele's dating are correct, then Hezekiah's reign would begin in either 729 or 727 BCE. On the other hand, states that Sennacherib invaded Judah in the 14th year of Hezekiah's reign. Assyrian records date this invasion to 701 BC, and Hezekiah's reign would therefore begin in