The ICBM (commonly known as a nuke) is basically a nuclear warhead, capable of massive damage over a widespread area. It's damage can be reduced by building a Radiation Center.
The missile can be made and fired from the Nuclear Silo which can be built only after 60 minutes mark. Overall preparation and production costs are whopping - measuring $1280 (2 Nuclear Plants, Nuclear Silo and The ICBM). Time of building the silo and the missile is also very long so watch out if you're not patient. The farther is the target the longer will the missile fire. Deals massive damage around the area of detonation. This should be used before a large raid or after to clean up left over buildings if your troops have been killed.
Be aware that if the enemy moves his army away from the nuclear cloud before it vanishes, the units will not take damage. The missile also has health, so if four or more railgun cannons are near where you want to fire the missile, the ICBM will be shot down without an explosion. Try sending an army just before launching missle so the railguns lock on to army while the missiles take out the railguns. Army health does not matter as it's almost always a one hit kill, so it is recommended that someone attempting this use light soldiers as they are cheap and not the slowest option.
- Select the missile in Ctrl. Units.
- Go to Interface.
- Click "Enable"
- Click on the ground where you want it to fire it.
- Watch it launch and cause a nuclear mushroom where you clicked. (Causes 200 damage to everything and does about 100 if they have radiation center)
It takes a total of about $1280and 10 minutes to make one ICBM and one Nuclear Silo.