Game Chishiki de Saikyou ni Natta Mob Heishi wa, Shin no Jitsuryoku wo Kakushitai

A lowly gate guard, just another nameless soldier—but secretly, he was the strongest soldier!? One day, Silva realizes he's been reborn as a mob soldier in the very game he was obsessed with in his previous life. To survive in this dangerous world, he uses his game knowledge to become incredibly...

Source: MyAnimeList