C. F. Keil and Franz Delitzsch on 2 Chronicles 27:5

2Ch 27:5

He made war upon the king of the Ammonites, and overcame them. The Ammonites had before paid tribute to Uzziah. After his death they would seem to have refused to pay this tribute; and Jotham made them again tributary by force of arms. They were compelled to pay him after their defeat, in that same year, 100 talents of silver, 10,000 cor of wheat, and a similar quantity of barley, as tribute. לו השׁיבוּ זאת: this they brought to him again, i.e., they paid him the same amount as tribute in the second and third years of their subjection also. After three years, consequently, they would seem to have again become independent, or refused the tribute, probably in the last years of Jotham, in which, according to 2Ki 15:37, the Syrian king Rezin and Pekah of Israel began to make attacks upon Judah.