spring to defense
spring to (one's) defense
To begin defending one very quickly or abruptly. I appreciate the thought, but I don't need you springing to my defense every time someone starts arguing with me. Thankfully, a group of people in the bar sprang to her defense when the man started assaulting her. The boss singled out Jonathan when he started criticizing the progress of the project, so I sprang to his defense.
spring to someone's defense
Fig. to go quickly to defend someone. (Can be against physical or verbal attack.) Fred was attacked and Ralph sprang to his defense. We sprang to Mary's defense when she was accused of doing wrong.