There are never blanket solutions in axis and allies, ever. Don’t look for them - or it’ll be your end. There is never a silver bullet.
Like any battle in time, there are MANY different tactics, tools, and methods you can use to achieve victory. The longer you play Axis and Allies, the more of these you will learn, and the more of these you will employ. Eventually you’ll find which ones you prefer, and what works best for you.
AXIS AND ALLIES IS A GAME OF ECONOMICS, PERCEPTION, POSSIBILITIES, and PROBABILITIES. - And how you choose to coordinate them.
None of it is ever as simple as what’s right in front of you, and despite the very rudimentary -this is what to do in this exact situation- kind of advice, the best thing to learn, is just what to do in general. Playing more games will always add to the choices available for you in your tool kit. Sometimes general strategy from history can help you understand these concepts.
Specifically, in reference to your question, I want you to consider the Vietnam war for a moment.
Are you the Yankee’s? Or are you the Viet Cong?
If you are vastly superior financially, then one LARGE battle is likely to suit you better than many smaller battles. And you’re going to want ALL of your forces, to fight the entire piddalance of your opponent, so that you can achieve victory.
If you are the guerilla force, or being overwhelmed, you want to survive as long as possible, where/however possible, until help can finally arrive. You also want to force match-ups, where you only face elements of your opponent, with your whole force, as opposed to the entirety of your opponent with his force.
Again, Axis and Allies is a game of economics. You make money at the end of your turn, but you also make money, when you destroy enemy units. The gamble is making sure through the exchange that you make more money than they did.
Specifically in reference to your second picture.
This type of stupa-stack is a tell tale sign of someone very new. Thus - you must attack outward in every direction. (especially considering you have some planes) Obviously there must be a german stack to the west somewhere looking to march down your throat, but there’s no sense in letting them, or the italians keep all their tanks alive, and have the freedom of mobility they want - whilst also reducing your income.
Possibly the only force I might not attack is the one in Smolensk, simply because I’d want to do well in the other locations, and force those infantry to attack me.
Also, in that situation, if you’re smart, you might even be able to threaten Karelia with liberation, by maximizing your position. As long as no blitz can hit your capital, use your forces to threaten other targets. Thereby forcing your opponent to react to YOUR terms, even though you have a smaller force.
It can be a game of chess… review the exchanges, and make sure that you’re getting a knight, when they get a pawn, ESPECIALLY if you are behind. And if you are ahead, obviously you want to 50/50 trade pieces, or better, until your opponent has nothing left.
There’s alot more to it than that, but no one wants to read a book on the subject, over the forum.