Hiraheishi wa Kako wo Yumemiru

After a long battle, John Celias, a soldier of the Demon punitive force, sees the hero topple the Demon King at last...and he is defeated by the remnants of the enemy. When John, who should have died in the war, wakes up, he finds that he has become a baby in his hometown... the same hometown that should have been destroyed by the demons. John realizes that he has actually gone back in time and decides to use the fighting prowess and the knowledge he gained in his previous life to change his tragic fate! It's a story of a soldier and his time travel counterattack fantasy!

(Source: AlphaPolis)