Originally posted by the Bear:
if the 1994 version is anything to go with, turrets are key to defense.. they will take out the Ordos before they come near your base..
use the bigass tanks to whack their chem missile tanks as they cannot fire short distance
The 2000 version is pretty different from the 1994 version, from what I know...
Yeah, well, my armoured column ran into a huge Ordos armoured column when I was returning to base after I had decimated the Harkonnen base.
I wiped out the Ordos armour, but at the cost of many of my own tanks. They used the chem missile tanks to subvert several of my units to their side. Luckily I saved the game just a few minutes before.

This time I managed to get them back to base just as they were sending their armoured columns out... but I still lost quite a few tanks as the Ordos kept throwing their armour against my base defenses.
And they keep rebuilding whatever I destroy with my Ornithopter airstrikes.

In the end, I've just managed to destroy their Construction Yard... it cost me my entire Fremen army and an airstrike, but at least now it's just a matter of time before they lose, since they now can't rebuild what I destroy. I'll keep wearing them down with airstrikes before sending a massive armoured column to destroy the base.