Pity Poland. Pity poor, poor Poland. With inferior tank and plane designs and almost no navy except for advanced diesel submarines and heavy cruisers, there is so little Poland can achieve. In terms of tank warfare, its tanks don't have the expected bite that can be expected of the French-styled R35, and in the air war it can only field but a handful of antiquated weapons.
But with this, is Poland defenceless? the answer is no.
But it will take a lot of nerve from you to win.
The first thing to realise is that Poland benefits from two areas: food production and wonder racing. Food is important for creating early rush units, especially cavalry which requires a lot of food. Like Germany, Poland can raise Uhlan Lancers in the early part of the game, which can then later be upgraded into the dreaded Wileńska Cavalry Brigade for maximum damage. These units are exemplified by their fast gait, and destructive attack, allowing them to work as hit-and-run assassins, especially against enemy infantry and/or limbered units.
The next thing to note is that Poland has 3 additional game-winners: the wz35 heavy rifleman, and the TKS class of tankettes, consisting of the TKS-3 and the TKS-d. Although the TKS-3 and TKS-d have lower attack, they like Poland's fearsome horse units have excellent rates of fire, as do Poland's sole antitank defence. It is true that tankettes suffer from problems - they can't seem to make up their mind if they are armoured cars or tanks, and are far more inaccurate than both - but they have one ace up their sleeve: they have more hitpoints than an armoured car, and also are fairly mobile, making them useful for one thing: raiding and attacking light units. Couple this with the Polish propensity for heavy rifles, and they can prove to be very deadly, especially if fighting against nations which are reliant on the late game or on booming. Enemies producing more oil than you? send some horsemen to kill their workers. Worried about Germans or Soviets knocking at your door? force them to invade and commit, then use your superior tankettes to swarm and destroy their forces before the tanks can roll in. Enemy already has heavy tanks in place? separate them from anti-air support and use your P-25s and artillery to silence them.
Thus the Polish strategy is to strike first, and hard and fast at that. Destroy soft economic targets using your powerful souped-up tankette and cavalry battalions. The only problem with Poland however is that once its prematurely ageing war machine reaches the higher trunk technologies, it will start losing steam, with only French and British airplanes helping to keep Poland aloft. In the late game, Poland is little more than a sitting duck, with factions such as Romania and/or Argentina capable of more than mopping the international floor with Poland — either a powerful blitzkrieg using modern weaponry or several atomic bombs will finish off Poland if you are unlucky.
In which case, Poland has another card up its sleeve: wonders. Because Poland can build 2 wonders per city, and also has a food production bonus, Poland can choose to go for a wonder-based strategy, but this will require very good diplomatic skills on your behalf. To go for a wonder-based strategy, always research the Fascist triad of governments (Hierarchy; Collectivisation; Militarism) to maximise the number of wonders available to you: one wonder owned by you is a wonder your enemies can't build. Although wonders can be parcelled away in "safe cities" strategically located far from enemy lines, it is not a failsafe strategy as your opponents can rush bombers in to destroy your wonders, in which case consider making allies and toughening them up with food. Britain and France are natural allies for Poland — food can be sent to Britain to gain "interest" to build up infantry and infrastructure (cities require food, timber and oil to be produced) in anticipation of a war economy or to finish wonder construction; France is also useful in a co-op strategy in wonder production, especially if it is aligned to liberalism: both France and Poland can complement each other (and we're not just talking about uniforms). Thus, Poland is a risky but potentially rewarding faction to play. It can either be used for early game rushing, or wonder booming.
- Cavalry: Uhlans, Wileńska Cavalry Brigade
- Special forces: Chłopskie Militia => Armia Krajowa
- Anti-armour: wZ35, has a good rate of fire.
- Special forces: Armed peasants# [1-2] => Peasant guerillas#
- Tankette: TK3 
- Light tanks/tankettes:FT-17^ => 7TP 
- Heavy: Mk VIII Liberty^
- TKS-d 
- Bofors 37
- Sherman Firefly  (requires Capitalism)
- Tachanka  => SP wZ.34  A Polish armoured car
- Armed caravan^
- Armed merchant^
- Armed supply truck/Halftrack: Universal carrier 
- Flamethrower infantry^
- Fighter aircraft: Biplane  => PZL P11  => Morane-Saulnier M.S.406^ 
- Bomber aircraft: Airship => PZL 37 [4-6]
- Attack aircraft: Bristol Blenheim# 
- Can build an extra 2 farms per city, +10% Food Commerce Limit.
- Farms generate +2 wealth.
- Start with a granary and receive Granary upgrades for free.
- Wonders cost 25% less, and you may build two per City.
- wz35 and TKS-d have higher rate of fire, vis-a-vis other units (ie Tankgewehr and other tankettes)
- -1 attack on all unique units