[spring] to {one's} defense

to quickly come to the aid or support of another person when they are under attack, criticism, or facing a difficult situation

When her friend was falsely accused, she sprang to her defense with evidence to prove her innocence.
The loyal employees quickly sprang to the CEO's defense when unfounded rumors about the company spread.
He sprang to his brother's defense during the argument to protect him from harm.
The teacher sprang to the student's defense when they were unfairly criticized in class.
In a crisis, it's heartwarming to see people spring to each other's defense, offering help and support.