Albert Barnes Commentary Numbers 32:39

"And the children of Machir the son of Manasseh went to Gilead, and took it, and dispossessed the Amorites that were therein." — Numbers 32:39 (ASV)

The children of Machir - Machir, the son of Manasseh, was long since dead: even his sons had been brought up upon Joseph’s knees (Genesis 50:23). But the renown acquired by his descendants raised his family almost to the dignity of a tribe; and the Machirites are in the next verse styled Machir, just as the children of Judah or of Ephraim are often spoken of as Judah or Ephraim. So in (Judges 5:14) Machir is coupled with Ephraim and Zebulun.

Went - that is, “had gone:” the statement is preparatory to the ensuing record of the grant to them of the land they had won.

Gilead - More strictly part of north Gilead; which, though inhabited by the Amorites, had belonged to the kingdom of Og. Gilead was the district from which had sprung the ancestress of the Machirites (compare 1 Chronicles 7:14).