Boris is present and quite capable of doing most of the work here. Keep him escorted by some tesla tanks though or you may regret it (sadly Boris seems to die a lot by IFVs and gatling tanks). Begin your assault at the Allied base just across the bridge. Don't eliminate the whole thing though, just anything that stands in your way of getting to the beacon. Keep the tanks handy and if anything dangerous approaches Boris have him escape behind them while the tanks finish off the threat. Advance slowly and cautiously and you'll eventually be in range to use the laser on the beacon. Your successful airstrike will turn the Allies to your side.

Now I recommend building some grizzly and tesla tanks to escort Boris to the Yuri base to the northeast (you can begin the advance as soon as battle control is online as you start with plenty of tanks to get started). Keep Boris near the tanks still - you don't want him to die. I put Tanya on guard duty with the tanks. She can use C4 when it's a good time. Target the power plants with the laser and have the tanks and Tanya destroy any target of opportunity. Namely any gatling cannon that stands in boris' way of finishing off this base. With enough power plants down the base will lose power (psychic towers will stop spinning so it's easy to see) and you should use the tanks to finish off any military buildings while Boris targets the Dominator. Not very hard at all. When the dominator is destroyed Yuri will send everything he has left at you which shouldn't be much.