None of us could do that, I'm afraid. But in every war, there are combatants that do what they can....which is better than doing nothing. And I suspect that.... the pent up anger and frustration, over these past decades, should act as a sort of adrenaline rush to help many keep up. And never underestimate the power of adrenaline. For some of us that haven't felt that rush in decades.... it could kill us! lolol
If you consider the 'three for me' idea, that could have a serious affect, especially with accurate long distance fire.
If you don't have the tactical mobility of your adversary, rely on stealth, distance, cunning, your knowledge of the terrain and the area, and keep them at arm's length or further rather than let them in close. Don't play to their advantages, play to yours. Blend in. Be invisible in plain sight.
The atrocities which inevitably follow will strengthen the resolve of others, it's how we Americans are wired. The adversary will lose.
An army of active grandkids (and great-grandkids) keep that adrenaline rush not so far away. Under that influence I can move like I did in my 20s, I just can't move that fast or lift that much all day like I could then.