For King and Country

Your units are your eyes, your sword and your shield. Each unit on the map represents a group of loyal, determined and fearless soldiers, all of whom have taken up arms in defence of your esteemed empire. They will defend your borders, seize and hold territory, scout enemy positions and ensure your dominance on the global stage.
Each unit has two circles around them, representing their visual range. The outermost circle, which will appear lighter than the fog of war, but darker than the inner circle, will show the positions of enemy armies in range. These will be represented by a collection of translucent sprites, with a question mark. This means that although your troops have reported the presence of an enemy army group, they are not close enough to identify numbers or troop types.
Once a unit enters the inner circle, all details about the army will be made clear. You will be able to see how many units are present, their morale, and the troop types that compose the unit.
 
In organisational terms, they can be divided into three main branches.
 

Land

Your ground troops will perform the majority of the work on the battlefield. Ranging from rank-and-file infantry, to armoured cars and tanks, to artillery, these units will see action in all corners of the world.
Armoured cars, for example, have a wide visual range, and with their speed and armour, are well-suited to racing to the defence of your provinces, and patrolling your borders, while your tank brigades have no equal in breaking enemy defensive lines and forging a path for your infantry.
These units can also be supported by long-range bombardment from your artillery. Take some time to look over the troops you have available. Combined arms is the order of the day, so experiment with different army compositions and see what works for you.
 

Sea

Island nations receive this lecture early, and often, and other empires find out a little later in their campaign: You cannot rule the world without first ruling the waves.
Cruisers and battleships can bombard coastal provinces and shatter defenders without fear of retaliation, while submarines can ambush and destroy transport ships with ruthless efficiency, all while evading detection. Mastering the seas means you control who gets to travel where, and certainly should not be second-guessed.
 

Air

Air power was in something of an experimental phase throughout the First World War, with many commanders preferring to eschew the wood-and-canvas biplanes in favour of more traditional methods of fighting.
Those commanders would, of course, learn their mistakes the hard way. While vulnerable, very little compares to the impact of sustained bombing from the air, and your troops will have a far easier time advancing if the skies are full of your planes, and not the enemy's. Rely on your fighters to keep your airspace yours, and lean on your bombers when you need to root out some particularly stubborn defenders.
 

Combined Arms

No single brigade can bring you victory, and so you must master all of the options available to you to defeat your enemies and take control of the game.
 
Good luck out there, General.