Tips to Beat the Campaign
The refit phase is all you have in a campaign.
Learning how to preserve your force while dealing losses on the enemy is a key part of the campaign.
In modern/cold war battles, units cannot sit in a location too long.
To do so, risks getting hammered by artillery or airstrikes. Another mistake made is not finding and killing enemy recon.
Those units can hide nearby and provide accurate direction of artillery strikes on your units.
Look to have your forces dispersed and also on the defensive look to have a means of falling back to another good cover locations to avoid those artillery strikes.