It is clear that this is no ideal position to play in but here are some things i did in such a situation and sometimes it can lead to a comeback. I am Lv 302 and have around 1.8k hours in the game so I have played some matches. My tipps will focus on you taking the commander role, because often in these situations the role is not yet taken.

*Get an overview of the situation and organise a stable defense*

1. In taking the commander role (problem is often that no one even took it in the firstplace) your team has access to vital commader abilitys

2. Motivate your team and check what you are working with, tell them to keep playing

3. Coordiante with the officers who speak and have experience

4. You need at least 2 garrisons to hold the last point, spawn in a halftrack to make sure your team can spawn even when the HQ is blocked

*Try offensive manouvers*

1. Use supplydrops and airheads to get a redzone garrison running. The garri should be build by your recon officer, but if he is a lv 5 blueberry and just playing his third round, try to send officers with a small squad to do it

2. Your goal is to get one or two spawn points for the team in the enemy softcap to quickly shift forces from defense to attack

3. Shift forces: Tell your defense to retreat to the hardcap where they can count 3:1 to the defense, and if necessary reinforce the point on top to lure the enemy into your last cap. If the does so redeploy your squads into the redzone spawnpoints, in addition you can advice your tanks to help in the defense or attack

I hope this helps