That's Jack Churchill. Here are a couple posts to get you started:

• Did Jack Churchill really kill a man with a longbow during WWII? - featuring /u/estherke. This post has been archived, so if you have follow-up questions for any of the users, just ask them here & mention the relevant user's name to notify them

• How were people like Jack Churchill allowed to carry a sword and longbow into a WW2 battle? - a recent post featuring /u/nilhaus