Antonyms for laying down arms are taking up arms, arming oneself, defending oneself, and fighting back. While laying down arms denotes a gesture of peace and surrender, taking up arms means going to battle, standing up for oneself, and taking a stance against an enemy. Arming oneself connotes the act of preparing for battle, equipping oneself with weapons, and developing strategies to outsmart the enemy. Defending oneself signifies protecting oneself from harm, standing one's ground, and holding one's own against an attacker. Finally, fighting back denotes resisting the enemy, countering their moves, and engaging in a battle of wits and physical strength.