John Gill Commentary Joshua 11:15

"As Jehovah commanded Moses his servant, so did Moses command Joshua: and so did Joshua; he left nothing undone of all that Jehovah commanded Moses." — Joshua 11:15 (ASV)

As the Lord commanded Moses his servant, so did Moses command
Joshua
Which was to destroy the people of the land, (Deuteronomy 7:1Deuteronomy 7:2) ;

so did Joshua, he left nothing undone of all that the Lord commanded
Moses ;
both with respect to the destruction of the people, and of all their images, pictures, altars, groves, and high places; see (Exodus 34:11–13) (Numbers 27:18Numbers 27:19) (33:52) (Deuteronomy 7:1–5) (31:7) .