To Counterattack, if the enemy is within range the defender calculates the attack normally, taking into account any Dodge and Cover (section 5.1) modifiers. If the attack is successful the aggressor is destroyed. If the attack fails no losses are taken on either side.
Please note that Battery units, empty or Mortar-loaded Transports cannot counterattack.
When a Tank, Transport or Artillery is destroyed, flip it onto its roof, but leave it on the battlefield to act as a barrier (section 5.1).