Given the asymmetry of this game, I will share a few overarching tips and then a bit of colour for each of the three powers:
Using all three rounds of attack; The point of this note is that war is hard! War is really hard! If you are rolling as the attacker you want to have a decent dice advantage but even then you may not get the number of hits you need in just one turn. If you don’t then you will need to go again, and you don’t want those troops stranded and waiting for reinforcements. There is one exception to this which is as the axis – preventing building in France by sacrificing troops into long battles as this prevents the West building in these locations.
Using Wildcards; In the diplomacy phase there are wildcards that allow you to immediately effect the map (not wait for the end of the turn) in one of a few countries. In the first turn these are almost pointless, but later in the game these can build influence in countries quickly and in combination with the normal diplomacy cards. Stealing resources through using wildcards for attacks can also be very effective to switch control of a region from an opponent to you (and not just neutral) in one turn. Hold these back, combine them, and steal a charge on your opponent!
Science and the economy; Lot’s of games will be won by the default victory of the highest production, and some games will reach economic victory – reaching 25 victory points at the start of a turn. Your basic production is your basic victory points (just like Terraforming Mars!) but you can add to it with any atomic technology. Building atomic techs therefore boost your chance of winning, but also help you build towards a victory where that 4 part science is an automatic victory (subject to minor placement conditions). Actually achieving a science victory is very hard, but building towards it is a good way to grasp the economic win!
Tanks + Infantry; It’s a little statistical fact, thanks to the BGG forum thread on this, that a tank plus an infantry is the way to land the most hits in a fight. However, attacker be ware – you will also lose more units on average over time through this method. Attacking with this combination provides the advantage of “going first” but losses you the better chance to hit of infantry and it leaves you exposed to counter strikes over time.
Interventions & Partitions; When your opponent invades another country you have two interesting options. If you are not at war with them, you can steal the rest of the country without a violation of neutrality – without handing cards to your opponent. Alternatively if you are at war with that rival then you can gain that country and units immediately by bringing one land troop in and intervening on it’s behalf! Great resource boost in the fall (before production!)
Playing as the West;
This is a moderate complexity role in the game – you start weak but with the addition of America you will become very strong. If you are playing as the West it is key to defend the French border. Boosting the troops, adding infantry and providing a protectorate status to the Low Countries are all key ways to stop the German invasion early in the game. Add to these areas a chance to build industry (two per turn) unless you get atomic science and you have a strong chance of a win in the late game. You will in the future struggle to get population and resource due to the map – your best chance of population is the Nordics and your best chance of resource is Persia. Given this, open your game with real units in India at first and not forts as you may well need them! Lastly, if you are going to push for the military win, then it’s worth looking at two options – the naval assault on Rome or the control of Denmark as a route to Northern Germany!
Playing as the Russians;
It’s likely to be a slow build but watch out for the Axis taking Rumania, Poland or Turkey – these are key states for you for resource, border protections or population respectively. Your factories will cost you a lot in the early game, but you start with more than the West and so this shouldn’t be too challenging. The Nordics are less relevant but plugging the sea in Northern Europe would serve you well – blocking quick movement into one of your capitals and potentially a way of losing the game. The Winter phase gives you time to move back to Baku, so in all likelihood you will be facing West and an aggressive player is going to seek to cripple Germany’s infrastructure and roll through – splitting a small force off to keep the axis building in Italy.
Playing as the Axis;
You are in a tough spot at the start of the game – you must expand, you must gain resources before war. Doing this, and going for war (which I think is your best option) is all about managing a combination of diplomatic absorption followed by military capture. Firstly, keep back your key diplomatic cards later in the turn – the West and Russians will force you to play out your hand early in the game, so try to delay showing where your strength is until they have started to play cards. Also, don’t waste cards on locations you will invade – often the Low Countries / Denmark / etc. Ideally, you invade low muster value countries because they give less cards to your opponent, but don’t hesitate to take key states with one opposition influence – after another diplomacy round this might become impossible to take without starting war. When you start the war, because you probably will, take the advantage of the first player turn first strike – this is helpful and a combined arms force including air force can usually overcome the French across three seasons if you have already got the Low Countries – but you want to use that first strike rule for Lorraine. Also, take Paris. It looks as though it’s the lesser benefit, but the rules state that the French army is then removed and the country collapses! As for the Italians – there are two functions available; blocking the Mediterranean to cripple the West supply chain, or to swing round and support Operation Sea Lion. There are more complex Axis strategies using u-boats or invading Russia from the south or raiding through the northern European map with a landing base in the small German state, but these are harder to achieve – one’s for later games!