Usage: 2 forms in 2 verses
Form Translated As     In Verse(s)
συνεπολέμησε joined in war with LXX.Josh.10.14
συνεπολέμει joined in war with LXX.Josh.10.42

Liddell-Scott-Jones

συμπολεμέω (sumpolemeō) to join in war with G:V

συμπολεμέω,

join in war, [Refs 5th c.BC+]