A pogrom is not a war between two armies. It is a planned, often sudden, attack on a group of people because of who they are — usually their religion or their people — in the streets and homes where they already live. A crowd is stirred up; shops and houses are smashed; many are beaten or killed. The police may look away, or even join in. The word came into English from Yiddish, and Yiddish had taken it from Russian; history books use it most often for attacks on Jewish families in the old Russian Empire in the late 1800s and early 1900s. Though actually, people now also use it for other mass killings of this same kind, not only that time and place. It is a heavy, serious word. You will meet it in history and in the news, not in everyday chat, and it is never a light joke.