I have received multiple requests for this training topic but admittedly have been dodging it. There's a reason for that--there really isn't a right or wrong way to defend against an attack. There is, however, a right or wrong way to defend for EVERY situation. I'll cover as many as I possibly can with various small tips thrown in to help. Just remember, no defense is truly perfect and no formation is infallible.
There are some basics that must be understood to proceed. First and foremost, you cannot properly defend unless the heroes standing in the city are filled properly. All heroes standing in defense MUST have at least one troop per box. If you fail at this, you can kiss your bonuses good bye while the attackers flanks wreck havoc on your formations. Second, Walls and Towers should be upgraded to the max to assist against stronger heroes. Third, every city that will defend needs a mayor and that mayor needs gear that specializes in DEF to improve the effect. Also, your mayors should have the middle column of the Politics skill chart finished before anything else to assure you that you can survive.
Other basic tactics include the number of heroes you use. Generally speaking, it is best to have a multiple of 3 for the number of heroes defending. Your enemy cannot send more than 3 so that way you're meeting them on as even ground as possible. IF they send less, you have an advantage for flanking. By going with multiples of 3 (6,9,12, etc) you guaranteed that you continue to face them on even terms, increasing your chances of survival.
A popular question about defense is what formation to use. Well, there isn't a single answer. Every player must determine that according to the strengths of each individual hero. If being attacked by someone you have faced before, try to recall how they sent their heroes and make adjustments to your own formations to counter. Sometimes you may want to meet them box for box, other times, when you are at a disadvantage, you may want to knock out their small boxes first. This normally can't be predicted and is up to you to configure on your gut instincts and past experiences.
Larger players often use formations that compliment their scrolls, thus stacking the middle 3 boxes. This can be countered in many ways, but splitting your boxes with your small quantities spread into middle boxes doesn't actually accomplish much except delaying the inevitable. If you choose to fill the middle 3 as well, be sure to put MORE THAN 1 troop in your end boxes. This way, if some survive, you still have flanks intact for a second wave of attacks. Also, if you utilize the First Aid scroll on your mayor (recommended), you will recover some of those lost. Because level 3 and 4 First aid give 9% and 12% back at the end of the battle, you will need to put more than 10 in each box so that you recover at least 1 troop in your troop boxes in the next wave. In times of war (now) if your mayor has a scroll slot open, no other scroll should be on there before First Aid. It won't win battles for you, but it gives you a chance to take some more troops down with you in a losing battle.
Most of the time when you're under attack, the aggressor is stronger than you are. There are some tactics that may allow survival. One of those is the 3 /3 breaker/power defense order method. This is widely used by players that have decent heroes but still find themselves at a disadvantage. Here is how the defense order works.
First, you need 6 heroes. Three of those heroes need to be your power--the real defenders. These would be the best you have available and need to be in proper war formations. The other 3 heroes can be weaker because they have only one goal--breaking the formations on the attackers so your power hitters can clean house.
The first step in this defense is to put your heroes in an odd formation. You will want to heavily stack your end flanks (or whatever boxes match your aggressors small boxes) while putting as little as 1 troop in the other boxes. If you know that your attacker likes to fill another box as a half filled box most of the time, concentrate your remaining troops to match that. These heroes do not need to be filled completely because their goal it to die, but take out flanks for your bigger heroes.
In order to do this properly, you need to click on ARMY at the top, then DEFEND on your left. Change your battle order from there. Most likely you'll be setting it in either FORCE or TROOPS in POSITIVE order, which puts your weakest out there first. This tactic won't always win because of the other factors involved, but it does increase your chances dramatically.
When setting up formation breakers is not an option due to excessive amounts of troops or heroes you must adjust your defense order once again. When you are logged off with multiple heroes in a city it is often best to lead with your strongest heroes. This forces you to once again make changes.
There is 3 options for how your heroes will defend. Those are by FORCE, TROOPS, or LEVEL, in either positive (weakest) or reverse (strongest) order. At first glance they appear to be the same but once the second wave of attacks comes through you will clearly see that they are not. For instance, if you were to set them by Reverse Level, no matter how many attacks hit you, the same exact heroes will defend first until they are dead. That means that if they only have the 9% remaining because of First Aid, they will remain your first defenders. However, if you were to set that by Reverse Force, the heroes with the strongest remaining attack power will cycle to the front lines with every wave.
You can most easily manipulate your defense order by choosing the TROOPS option. Say, for instance, you have 6 heroes that are all level 50 and all use either Snipers or Destroyers, the Destro heroes would fight first in Reverse order and last in Positive order because they have a stronger Force rating. If you want to stagger how the heroes defend, switch to TROOPS and take a few off so that every hero has a slightly different amount. This will allow you to determine your own battle order and the loss of just a few troops in your formation won't make a huge difference.
