But Ukraine’s engineering units are so depleted of men that responsibility falls to local authorities who use infantry brigades as contractors, with a small number of engineers overseeing work on the first line of defences.

So are they saying “contractor” in the sense of delegating work or “contractor” in the sense of “getting paid to dig trenches”?

Because like… its should be a normal thing to expect infantry to do a chunk of the manual labor alongside the combat/construction engineers when digging in.