The military forces of the Seven Kingdoms refers to the armies and naval forces employed within and by the Seven Kingdoms.
There is no single unified Royal Army, although the creation of one has been suggested by King Joffrey Baratheon. Instead, each lord raises his or her own military force as needed (via a levy) and places it at the disposal of their liege, extending up to the King on the Iron Throne. The result is a hodgepodge of forces, some highly trained and well-equipped, some consisting of little more than peasants armed with sticks. The population and size of each lord's lands also varies immensely, meaning that the size of the forces available to both individual lords and to the Great Houses as a whole can also vary significantly.
There are several standing military forces. The Royal Fleet and other naval forces require significant numbers of trained, specialised sailors, and are maintained at readiness at all times. The largest standing ground forces make up the City Watch of each of the major cities. The Night's Watch is arguably the most famous standing army, consisting of almost a thousand men manning the Wall against the threat of a wildling attack. The smallest, but well-known, is the Kingsguard, a force of seven elite knights sworn to defend the royal family.
Known military forces of the Great Houses
House Stark initially raised 18,000 troops to fight in the War of the Five Kings. These have been swelled by the addition of 4,000 troops from House Frey, and an unknown number from the other houses of the Riverlands. 2,000 men were lost (killed or captured) at the Battle of the Green Fork. The Starks have since won a significant number of victories, but it is unknown how many men they have lost in the meantime.
House Lannister initially raised 60,000 men to invade the Riverlands. This army was divided into two roughly equal halves, one under the command of Lord Tywin Lannister and the other under his son, Ser Jaime. Tywin's force defeated the Starks at the Battle of the Green Fork, but this was a feint. Jaime's army was defeated at the Battle of the Whispering Wood and put to rout. A third Lannister army, assembling at Oxcross, was then smashed by Robb Stark's forces. Tywin's army fell back on Harrenhall and then moved to King's Landing to engage Stannis Baratheon's forces. Tywin's army arrived late in the battle and helped rout Stannis's forces. Their casualties are unknown.
Renly Baratheon, supported by House Tyrell, raised an army of over 100,000 from the forces of both the Reach and the Stormlands and marched on King's Landing with it. When Renly died, many of these troops went over to Stannis but others remained loyal to the Tyrells. After accepting an offer of alliance with House Lannister, they combined with Tywin's forces to destroy Stannis's army at the Battle of the Blackwater. The number of the forces after the battle is unclear at present.
The "Royal Army"
The Royal Army is a proposed military force, an idea of Joffrey Baratheon's before he became the King on the Iron Throne. According to Joffrey, the system of feudal levies used in the Seven Kingdoms is both primitive and inefficient. He suggests the formation of a standing, highly-trained army drawn from all corners of the realm. This army would be large, with ten thousand soldiers to be committed from the North alone and presumably similar numbers from the rest of the realm. Queen Cersei Lannister has identified several problems with this plan, such as the difficulties in using such a force to put down rebellions in regions where members of the army might have lived. Since becoming king, Joffrey has not pursued the idea any further.
In the books
In the A Song of Ice and Fire novels, the armies of Westeros are said to consist mostly of untrained smallfolk, mostly young men who would otherwise be working in trades or in the fields. For the most part, they are sent to war with a bare minimum of training, there to just make up the numbers. The various Great Houses differ in how they train and equip their soldiers, with the rich House Lannister noted for giving their soldiers better equipment and training in certain weapons, particularly pikes and crossbows. House Tyrell is said to more rely on overwhelming numbers, having a population almost double that of any of the other regions of the continent.
Mounted knights (heavy cavalry in the case of the North) are expected to undertake the bulk of the important fighting. Knights are noted for spending their whole lives training for battle and usually maintain their own weapons and armor, making them an efficient force for lords to employ. The only permanent military formations maintained in Westeros are the Kingsguard, the Night's Watch, the City Watch of the major cities and the household guards of each lord.
In terms of numbers, George R.R. Martin was asked to approve of a series of figures for the Game of Thrones Roleplaying Game, published by Guardians of Order in 2005. He approved the following figures as the numbers generally believed within the Seven Kingdoms, but noted that they did not tell the whole story, as some regions required more time to gather their forces (so Robb Stark could possibly have raised twice as many troops, if he'd had a lot more time to wait and was able to feed them all whilst they did so). He also noted that some of the figures may have been spread by misinformation, and indeed later confirmed in the text of A Feast for Crows that House Martell had inflated its own numbers so as to appear more formidable than they really were.
- The Crownlands: approx. 15,000-20,000 men and 210 warships.
- King's Landing's City Watch has 2,000 men (raised to 6,000 men during the events of the novels).
- The lords of Duskendale, Stokeworth, Rosby and other castles can raise between 10,000 and 15,000 more troops.
- Dragonstone and the surrounding islands can raise around 3,000 troops, about 400 of whom would be mounted.
- 50 ships of the Royal Fleet are based at King's Landing. Their flagship is King Robert's Hammer.
- 160 ships (80 of them full war galleys) of the Royal Fleet are based at Dragonstone.
- The North: approx. 40,000-45,000 men, negligible sea power.
- The North has a total fighting potential of around 40-45,000 men. The sheer size of the North means that assembling this force is difficult, and can be severely reduced by agricultural needs depending on the season. There are around four footsoldiers to every one mounted.
- The North's last major fleet was destroyed by Brandon the Burner. Since then the North has had no strength at sea, just a few defensive ships based at White Harbor. During the War of the Five Kings, House Manderly received permission to begin building a major new fleet.
- The Iron Islands: approx. 20,000 men, 400 longships, 100 war galleys.
- The Iron Islands can raise about 20,000 men, with almost no cavalry to speak of. Most of these men serve as raiders and skirmishers on their ships.
- The ironborn have over 500 ships at their disposal, the overwhelming majority of which are longships meant for coastal raiding, not pitched sea battles. The major exception is the Iron Fleet, which consists of 100 heavy way galleys dipping 100 oars or more. The flagship of the Iron Fleet is the Iron Victory.
- The Riverlands: approx. 45,000 men, negligible sea power.
- The Riverlands can summon approximately 45,000 soldiers. There are three foot to every one horse.
- House Frey can muster about 4,000 soldiers by itself.
- The Riverlands has no major fleet, just a small coastal force based at Seagard to discourage raiding. Barges, skiffs and river galleys can be found on the rivers, however.
- The Vale of Arryn: approx. 45,000 men, negligible sea power.
- The Vale can muster about 45,000 soldiers, with three foot to every one horse.
- The Vale maintains a small defensive fleet at Gulltown.
- The Westerlands: approx 50,000 men, 50-70 warships.
- The Westerlands can raise about 50,000 soldiers at need. The ratio of foot to horse is unknown, although Tywin Lannister favors having about two to one. The Lannisters' immense wealth allows them to buy, train and equip the horses such numbers require.
- The City Watch of Lannisport is extremely well-trained, and constitutes the most disciplined feudal foot levy in all of Westeros.
- The Lannisters also field exceptionally well-trained pikemen, which can wheel on command. Ser Kevan Lannister is known to command the pikemen in battle.
- The Lannisters command a coastal fleet of between 20 and 30 cogs, galleys and dromonds based at Lannisport, and an additional 30-40 ships based along the coast. Since the Greyjoy Rebellion, the Lannisters have ordered all coastal houses to have naval forces.
- The Reach: approx. 100,000 men and over 200 warships.
- The Reach can muster a well-trained army of 80,000 men. At exceptional need, this can be raised to 100,000. The Reach generals prefer a cavalry to footsoldier ratio of two-to-one, but this is not always possible.
- The Reach maintains an extremely large fleet at the Arbor, under the command of House Redwyne. This fleet consists of 200 warships which can dip 100 oars of more. The Shield Islands, the coastal houses, the Mander lords and the defensive fleet at Oldtown can all increase this number significantly.
- The Stormlands: approx. 30,000 men, negligible sea power.
- The Stormlands can raise about 30,000 men. They have a very poor horse-to-foot ratio, so most of their army is not mounted.
- Despite this, the Stormland forces are well-trained, particularly those based on the Dornish Marches.
- There is a small number of ships based around the coast, although there is a constant threat of storms smashing them apart.
- Dorne: less than 50,000 men, negligible sea power.
- Dorne presents itself as being able to raise 50,000 men. A large part of their army consists of spearmen. Their horses are known as "sand-steeds" and are best-suited to light, hit-and-run attacks using horse archers (which Dorne has more of than any other army). Later, it was revealed that Dorne had significantly exaggerated its numbers and military power to appear more formidable than it really was. The true numbers available to Dorne are not publicly known.
- Dorne has very few ships due to the lack of good anchorages along its coast.