With very little scripting you can make your guards much smarter and more realistic.
Try out this little mission. First attack the guards on the left and take out the patrols and the guard towers. Then try the guards on the right and see which ones you think react more realistic.

Stupid guards (left)
First off - when a building in Generals takes over 2/3s damage, then it ejects the units inside. But the units still stick around until the building is all gone. This means that you can just shoot up the building with a Tomahawk from a distance, and when the units exit, you switch targets and blow them up.
Also, even if you blow up two guards from a patrol of 10 units, the other eight just keep patrolling - now how smart is that?

Smart guards (right)
Take a look at what happens as soon as you kill or hurt just a single guard.
Also note what happens when the tower with the guards is destroyed.

Try the map, and then take it apart in WorldBuilder to see the scripting.

Get map, zipped