Reinforcement

We need reinforcement to protect our members. If we do not help our member we will be the next target.
Reinforcement can be effective if we have a lot of troops in city.
In worst case, enemy attack us by 100k archers (or 125k archers if use war ensign)  if we have same troops in our city and a good wall then we can win the battle.
I have seen that 15k arch towers with archery/engineering/machinery at level 10 can kill 100k archers if attacker archery is low.
There are some point that should be considered in reinforcement.

• Before sending any troops to other city make sure that our member's embassy is open to accept reinforcement troops.
• The city's gate should be open otherwise reinforced troops cannot fight.
• City should have high level embassy to accept more troops from other players. If embassy at level 5 then it can accept troops from 5 players or 5 groups of troops. There is no limitation in troops' size. but number of groups is limited to the embassy level. So, upgrade your embassy at least to level 5.
• Troops need food, make sure there is enough food in city, if not you should send food to the target city. If troops have no food to eat they will return automatically.
• Each group of troops need a hero. They fight separately, so you better to send a high attack hero.
• By a high level beacon tower, target city can foresee the enemy's troops and hit time which are great help when player need reinforcement.
• When you see red bird then go to Reports -- Enemy and inform our members in alliance chat box about the incoming attack. Then members can send their troops to help you.
• After finishing the fight recall your troops, or the target city can dismiss them to return.