Related Clues:

• Resistance reducer
• Ongoing trouble
• Alamo event
• Lunge
• Persistent attack
• WWII Leningrad event
• Rocket booster's push
• Prolonged assault
• Attack from all directions
• It may force a city to surrender
• Campaign against Troy, e.g.
• Encircling tactic
• Offensive action
• Attack tactic
• Battery mate?