討ち入り is read as うちいり (uchiiri) and means raid.
うちいり
uchiiri
うちいる
to break into (a house to kill the master)
とうぎ
debate
とうろん
うつ
to attack
とうろんかい
うって
attacking party
うちじに
death in battle
うちとめる
to kill (with a sword, knife, spear, etc.)
とうきゅう
investigation
とうぎりんりがく
discourse ethics
とうろんしゃ
debater
とうばく
attacking the shogunate