Attacking is not just to send out your army at someone and hope to be successful. You also have to find a target, and sometimes wait a long while before it opens up and becomes attackable.

How to find a suitable target
•Go to your sector in the menu, start browsing the sectors, and find someone who seems to be a suitable target. Or if you know of any target in some other way (for example because of friends telling you, or that you notice someone making an attack on one of your sectormates in the sector news), that’s ok too.
•If you find kingdoms which might be suitable targets, but which you won't hit yet, copy and paste their kingdom line and sector number (for example "3:11 Plains of Steel (x:4,y:3) Mystical Lands 5,678 1,540,301"), and any aditional info you have about them (like stats, or if they are SL), into a message which you send to yourself. Then check their kingdom every time they log in to your account, and compare it to the stats in the message to see if there are any changes.
•If you are big enough to attack top 100 kingdoms, just go to the score list a few hours after an update and click on each kingdom on it to see if they have gained land since the scores were taken.
•Another way, if you just have enough time, is to use the spreadsheet in the menu to the left (which is usually used for bank finding), but to search for kingdoms which have gained much land instead of which are possible banks.
•When you've found a possible target, go to Probe room and probe him for his military stats (SoM). Probing is described in the next chapter in this guide. The army is updated by hour change, so unless your target gets attacked, or attacks someone himself while you are preparing to attack, there is no use getting two SoM’s the same hour.
•If the kingdom isn't a good target yet, send his stats, kingdom line and sector number to yourself to keep an eye on it, just like described earlier, else continue to attacking it, described below.

How to attack a target sucessfully
•To do this in an easy way, click on "Calculator" in the menu to the left and fill in the correct values, then test if the attack will be successful. However, it can always be good to know how to calculate attacks too:
•Add your own bonuses (for planet type, military research, and so on) together. If you want to be sure about not sending more than enough, you can use probes to spy on shields of the target, otherwise you should always assume that they are on 10%, which is max. A target’s military shields lower your offensive power with as many % as it’s efficiency is, if you attack.
•Add all the defending kingdom’s bonuses together, multiply with his army. If you don't make a SoK probing, assume that he has power. If you don't spy on his research, assume that he has full military research, 30%. Those two probings are usually unnecessary anyway, since most kingdoms have power and full research, and if you expect them to have that and they don't, the only thing which will happen is that you send a little bit more military than needed.
Add all your bonuses together, multiply with your army. Then decide how much you will send. If that number (offense) is higher than the defender’s defense (multiplied with his bonuses), you will be successful. Else you will fail.
•If the target has a very weak defense, always make sure that you send 2x his land amount of offense points. That is always the minimum defense for a kingdom.
•If you want to be sure to be successful, always send a few % more military than needed. It is better to send 100 extra tanks and be successful, than sending one too little and fail, since unsuccessful attacks give you nothing at all, except for military losses.