When and why are soldiers charged with war crimes?

Soldiers are charged with war crimes during the war and after the war. They can be charged with charges of murder, ill treatment of or the deportation of civilian residents of an occupied area and put into slave labor camps or torture camps, killing hostages, and any act of wanton destruction of cities, towns, villages or any devastation not justified by the military or for civilian necessity. They cannot just do what they want in other Words. That is why the Japanese and Germans faced so many war crime charges. They violated the Geneva Convention and War Crimes Act.