Missile silos are the defensive game changer once you reach higher levels. A must have on any base in world war. But a pain in the *** to attack...
Basically you got three different choices:
1st. Burn baby burn - take it out early
a. Demolition (as many as it takes) plus mongols (can get upto +45% attack on your demolitions)
b. or Planes (most effective to send a fighter to clear out any SAMs, then follow up with a bomber to deliver the kill)
c. or Combination of a+b, typically several demolitions followed by a fighter to finish the job
For this to work, you gotta get good at recognizing the difference between a level 1 or 2 silo vs a level 3 or 4 silo. Until you get to stronger levels of demolition/fighters you might not have the power you're gonna need, to take out a level 3 or 4 (see option 3 below)
2nd. Silo, what silo - ignore that sucker
Say what?! Yup, seriously. Ignore it.
Find a place on the map where a high hit point army (a mix of generals, mercenary tanks, heavy tanks, regular tanks works best) will slowly progress somewhere useful, without hitting any anti-tank guns early on. What's gonna happen is that the silo is gonna light up like a Christmas tree, and then throw missile after missile at these guys. But sadly for the silo, nothing else is gonna happen. Those units have such high hit points that they can suck it up.
Meanwhile, put the rest of your army... wall miners, artillery, riflemen... somewhere far, far away from your big bait. Space them out so they don't clump together. Then let them move towards the silo without attracting its attention at all.
It takes a little practice to make this work, so try it out on some challenges vs the high players in your alliance. But when it does work, it's deeply satisfying.
Advanced strategies: Make life easier for your bait army, by using fighter planes to clear out any anti-tank guns that are in their way.
3rd. This isn't the oil you're looking for - move along, move along
Some bases, especially with level 4 silos and level 16 walls, just deserve your respect. Just hit 'next'. Or if it's world war, ask one of the higher guys on your team to deal the dirt...
Good luck buddy! Let us know how it works out for you?