Basic information on alliance war can be found here
If you are unsure about the specifics of alliance war, please do read the information from Empires and puzzles wiki on alliance war.
Hero analysis specific for Alliance war here.
Alliance war strategy No.1:
Tank Color Coordination
*refer here if you just want to know which tank color is the best now.
Many top alliances choose to coordinate the color of their tanks. The reasoning for shared tank color is to counter a common raid/war offensive strategy of doubling up attackers of the strong color against an opposing tank (e.g. bringing 2 blue heroes to fight Ares, 2 purple heroes to fight Guinevere, etc.) Should opponents attempt to double these colors, they will quickly run out of them in the first few rounds. This leaves the second round with no heroes of the strong color and the tanks will be more difficult to beat.
Flank Color Coordination
Some alliances choose to flank their tanks with 1 or 2 heroes of the complimentary color to the tank selection. This means that the color that is strong against the tank is weak against the flank. For example, assign green flanks behind red tanks so the strong blue tiles against the tank are less effective against the flanks.
Note: It is very hard to determine how effective these color coordination strategies are. There are precious few data to support this, so common sense and anecdotal evidence is what we have to go on.
*Excerpt from here. Do note that some information in this article is outdated/inaccurate.
Alliance war strategy No.2:
The key to winning wars is to have the highest average score/hit (assuming all hits are utilised). In order to do so, your objective would therefore to be able to have as many one flag kills as possible. In top alliances, one flag kills are easily obtainable as they have a deep bench of fully leveled 5 star heroes that can take down opponents easily.
But what if you don’t have such a deep roster?
Here’s a war strategy that you can utilize:
“Farming” the weakest opposing teams as many times as possible, while minimizing the number of times that you have to take on strong opponent teams.
At start of war (0-2hrs) target the 5-10 weakest opponents,
After first wave of respawn (8-10hrs) take the same teams down again.
After second wave of respawn (16-18hrs) take down the same weak teams again.
After killing all weak enemies, proceed to target all other enemies, as you will no longer be able to farm the weak teams again, until you reset the board (by killing all opponent teams).
The benefits of doing these are: Minimising attempts to take down strong teams, which will most likely take up multiple flags.
We can create different scenarios to see how this strategy plays out.
The following assumptions are made:
30 member alliance with all flags fully utilised (180flags)
Tough team takes an average of 1.8 flags to take down.
Weak teams takes 1 flag to take down
Each take down is worth 53 points.
We can compare 2 strategies.
1. All out attack to reset as many times as possible.
2. Farming weak teams.
In scenario 1,
To fully kill all 30 players would require 10 flags + (1.8*20opponents = 36 flags) = 46 flags.
That would give you 3 full resets for 1590 points + 42 flags remaining.
Assuming you take the 10 weakest team out for 10 flags for 530 points
and another 23.3 teams (42flags/1.8flags). That would give you
Total score = 1590*3 + 530+1237 = 6537 total score
Average score would be 36.32 per flag
In scenario 2,
First wave – 10 flags – 530 points
Second wave – 10 flags – 530 Points
First reset – 46 flag for 30*53 = 1590 points
Second reset – 46 flag for 1590 points
Third reset – 46 flag for 1590 points
Final Board – 22 flags remaining, points = (53*10 + 53*12/1.8) = 883 points
Total flags = 180
Total points = 530+530+1590+1590+1590+883= 6713 total score
As you can see, farming the weakest team strategy edges out other strategies by a slight margin, how big the margin is doesn’t really matter. A win is a win.
So all that is left is passing this crucial information to your alliance mates for your formal alliance war strategy.
Good luck & have fun in your upcoming alliance wars.