volunteer(a person who offers to do, or does, something (especially who joins the army) of his own free will • If we can get enough volunteers we shall not force people to join the Army); voluntary
volunteer fighter(Newly collated evidence documenting Russian military involvement in the conflict in Ukraine will be used to bolster legal claims against the Russian state by Ukrainian volunteer fighters.4uzhoj); voluntary recruit(Australia relied solely on voluntary recruits to serve in the AIF.gov.auTamerlane)
gov.au Tamerlane)