Declaring War – it sounds scary, but it’s fairly easy.
Find the alliance you want to declare war on. View that alliance page, and tap the Diplomacy tab (the third icon that looks like a scroll).
Tap the “Declare War” option. VOILA! You just started a war.
Here is the message your alliance mates see when war is declared.
Now your alliance will get the Alliance Bonuses that only apply to war, such as the Attack Travel Speed, and the Wartime Looting Bonus.
Be warned… starting a war usually means that outposts and villages are fair game… as is mass attacks, double and triple hits, and lots of sabotage.