China

The Best GDP and IC to manpower ratio. Plenty of land leaders and reserve manpower. Very high allegiance to the Soviet Union and enormous amounts of Unity. Operating throughout all of mainland China

Communist China is one of the hardcore large countries to play. You could be accidently lucky with a lot of campaigns with this nation.

Technology
Don't wait to upgrade at the end, instead, upgrade each Corps as they are deployed, and before the next corps is placed in the build queue.

Has hordes of infantry as the backbone of their army.

The army will need Blitzkrieg 1, Mass Assault 1, Infantry Warfare 1, and Assault Concentration 1 before setting out to do battle.

Once war breaks out, research combat medicine and first aid to help reduce casualties.

Keep Production Efficiency in the queue or at the top of the queue until your down to your last Corps.

Distribution of Leadership
Split leadership between diplomacy and espionage until you have ten (10) domestic spies and 40-50 diplomatic points.

Focus like a laser on technology during the build cycle. During periods of upgrade (in between building corps) switch all leadership to officer recruitment (using the 3-yr draft), until reaching 140% officers while still growing the army (at least 100% later on). Switch back to technology once the upgrade cycle is complete (or reaching 140% whichever comes first).

Diplomacy
Don't go to war with Japan in 1937 or you and America end up duking it out.

Alliances
Soviet Union

The Nation starts out as a friend of the Soviet Union. They can declare war on Germany together however China must consider this because it with Hitler will only end up in bloddy stalemates.

Other communist nations are allies too.

Decisions
If you elect to war with Japan and America to help protect North Korea or your other satellite States. You might get lucky with that with or without Soviet help.

Politics
Communist China should flirt with the Soviets for the game, although that might be the case China could get other allies

Ministers
   

Laws
While in the build cycle use Heavy Industry and Volunteer Army. Then, for the upgrade cycle, use Consumer Product Orientation and three-year draft (or the highest level draft available).

Go no higher than Full Mobilization until you solve the energy problem, then go with War Economy.

When actually at war use Universal Conscription. If you are no longer building anything, reduce to Full Civilian Economy to save on resources and money.

Political Parties
Communist China is, in a word, Communist. Make sure it stays that way.

Intelligence
After the Japanese DOW in 1937, use spies to raise the Tokyo-Tehran pact threat levels. This should eventually induce your satellite States in serving you by making a protective barrier.

If you go to war with Germany then you might not be so lucky in their turf unless you get help from the Warsaw Pact and Soviet Union.

Economy
Boost up propaganda on citizens.

Trading
Asia (except China and their satellite states) has an energy crisis. To make it worse for them and better for you. Bomb best trade ports of netrual nations and make Japan and America responsible.

Industrial Production
Keep Industrial Efficiency always in or at the top of the research queue.

Go with Heavy Industry while building units, then switch to Consumer Product Emphasis while upgrading. Upon building a corps, switch to upgrade cycle and top-off your officer pool. While upgrading, switch to 3-yr draft, then change back to all Volunteer force for the next build cycle.

Military
The army of China is the best army ever known in Asia.

Army
China has a huge army consisting of trillions of infantry units, 1,000,000,000 artillery units, and 100,000 Cavalry units. China has a nuclear arsenal of 1,000,000 nuclear weapons.

Navy
China has a Navy the size of it's Infantry with 1,000 artificial islands as bases. It has tons of islands to choose for as colonies of Naval Domination, even with Cape Verde making options in the Atlantic. It has trillions of small fighter ships, trillions of submarines, trillions of destroyers, trillions of battle cruisers, trillions of Air force carriers.

Air Force
China has a brutal and gigantic air fleet consisting of trillions of fighter planes, trillions of bombers, trillions of paratrooper planes

War with Japan
Just getting the Communist Chinese into the fight without getting wiped-out in the process is a major endeavor. Don't bother holding Shanxi territory unless you can hold Taiyuan and Hohhot. The attrition will drain your manpower, even though they're core provinces.

The best time to make your move is when the Nationalist Chinese eventually begin to push the Japanese back. If you start too soon, the Japanese will get you, but if you start too late the Chinese will take all the prize objectives.

Strike due north with the objective of reaching the Mongolian Frontier. Hohot is a key transportation hub, you must get there before the Nationalists to have any hope of success.

(V1.4: You can now join the Comintern and gain transit rights in order to exploit the back door through Mongolia and create havoc in Manchuria. By War's end you'll want to control a province right on the Soviet border in order to insure trade from the USSR as its "neighbor.")

Use your light armor to maximum advantage. The panzers will gain territory and outmaneuver both the enemy and your “allies.” Be sure to replenish organizational levels before moving on offense, because the Japanese will counter-attack, and counter-attack hard.

Keep to the flank, always the flank, especially the western flank. Meanwhile, use your “allies” to cover your flanks.

Keep fighting until the Japanese are defeated. If the Nationalist's cut you off, then get transit permission and get back into the fight, taking as much territory as you can.

Reunification of China
There are many important aspects of the Reunification effort that should be considered individually and pursued concurrently.

Decisions
When playing HOI3: Their Finest Hour, you will not start in an alliance with Nationalist China. This will save you the step of breaking that alliance. The first thing you should do is accept the 'Prepare for War' decision (available to all nations with an effective IC of less than 30) which will lower your neutrality by 0.2 per day. Lowering your neutrality with this method is the best possible method for declaring war on unsuspecting neighbors.

Technology
The next thing you will notice is your lack of size and IC. But what Communist China lacks in size, manpower, and IC it more than makes up for in leadership. Use your leadership to upgrade your infantry. In Hearts of Iron 3, whenever given the choice between quality and quantity, always choose quality. Also focus your effort in upgrading artillery, which you might not yet have, but you will soon. Also, after maxing out domestic spies set to increase your national unity, send spies to Shanxi to increase their threat. Shanxi will ultimately be your first target. You should focus the vast majority of your leadership into research. Diplomacy will get you very little (further elaboration is available in the Trading section)

Military Composition
You need to focus in on land units, primarily infantry and artillery. You can expand into motorized divisions later in the campaigns, but in the beginning, focus in on infantry and artillery. Previously it was mentioned that Mountain Equipped Infantry brigades are better for Communist China, however, Mountain infantry is far superior to Infantry in the mountains. Given that the majority of China is mountainous, it is highly encouraged that you utilize Mountain Infantry if you can. Even if they aren't as good on plains as Infantry, the well-equipped Mountain Infantry of Communist China can still easily take on the pathetically weak ground forces of the Japanese Imperialists.

When you begin the campaign, you will have several militia brigades. First, upgrade those (strategically, of course) to regular Infantry (or Mountain Infantry if you want to build a professional Army). Next, build your divisions with 3 Infantry/Mountain Infantry brigades and 1 Artillery brigade. When starting the war, you should be able to procure approximately 10 divisions (in 2 corps) of the troops I just described.

As time goes along and you conquer your neighbors, you should make your way through the research to get to Superior Firepower. This will allow you to put another brigade in each of your divisions. Once you've researched it, add a brigade of Anti-Aircraft to each division of Infantry/Mountain Infantry. This will go a very long way when taking on Japan, as Japan will use bombers.

If you choose to invest your precious resources in an Air Force, focus on Interceptors and Naval Bombers. The Interceptors will intercept the Japanese Bombers, and the Naval Bombers will do wonders against Japanese Convoys and the Japanese Navy in the future war against Japan.

Trade
You will start with a deficit in power and oil. You can try trading for these deficits, however, it is unlikely that you will be able to make up for everything you are deficient. Obviously, you will want to research resources, and you should, but I suggest you don't worry about it. You'll ultimately run out of power after approximately 10 months. This will reduce your IC down from the 12 it will be at (given the laws you will enact) to 11. This is very negligible. And given that your war with your neighbors will start in early 1937, it's worth waiting it out.

Initial Strategy
Wait for the Marco Polo Bridge Incident before beginning any sort of campaign. Leading up to the campaign, defend your southern border with one of your 2 corps and use your second corps to defeat Shanxi. Once the Marco Polo Bridge Incident occurs, Japan goes to war with Shanxi and Nationalist China. You divide your corps into 2 groups and head north and east and quicky capture the 2 victory points at Hohhot and Taiyuan. Since Japan didn't exactly prepare for this war very well, you should be able to conquer Shanxi without Japan taking a single territory.

Once Shanxi is defeated, sweep your troops south and to the east to the Japanese Border and draw an imaginary line up and down, lining it up with the eastern border with Japan that you now share. Don't take any territories east of that line. Let Japan keep Nationalist China busy while you push south and westward until China is defeated. Make sure to set a war goal to conquer Nationalist China right away, otherwise the game will get all wonky about victory points and surrender progress. After the Nationalists are defeated by Japan and Japan seizes the Chinese coast, it will take around a month for the game to let you conquer the territory of China. I'm not sure why, but for the entire time, it will show Nationalist China with 100% surrender progress. It's annoying, but they eventually surrender.

Then, move your forces around Guangxi Clique and quickly conquer it. After the first is complete repeat the same process with Yunnan. Xibei San Ma will be the most difficult and you will need 2 and a half corps to take them out without screwing up your supplies and organization.

If you are familiar with modern Chinese geography, you will notice that, if you conquered Tibet and  Sinkiang, and then the Japanese Territory followed by  Mengkukuo and  Manchukuo, it would look exactly like China does today. I admire your keen observation skills. But don't do it. Declaring war on and conquering your neighbors will make you the predominant threat around the world until the Fall of France. Any higher and the Allies will declare war on you as they have territories on the Chinese Coast that you are threatening. That will screw everything up, especially if you are a Comintern member, because then the Comintern is at war with the Allies. Finland will probably join the Allies if that happens, and, given your lack of navy, you won't be able to project any power against their over-powered navy, let alone land troops in Europe or North America. Bottom-line: leave Tibet and Sinkiang alone.

The only thing left is to take on Japan. Use Infantry, and then Guard your ports with Garrisons (2 Garrisons Brigades per Division, one Division per port). Manchuria and Menguoko are easy, the Japanese won't have an as-upgraded Army as you. Especially if they are busy with naval engagements in the Pacific.

Factions
Obviously you should join the Comintern, but wait until the last moment. You don't want to get dragged into a war against Japan before you're ready.