Reserves/reinforcement in north

[History]

Why does robb not orders that another army be created before he marches to help the riverlands and rescoue eddard stark or after he defeats jaimes specially with the casualties of battles of whispering woods,battle of green fork,battle of  camps losings 5000+ troops ?he knows there still thousands of posible troops and that the extra troops can either reinforce him at the riverlands or guard the north against wildings, or ironborn raids and the lanister show that they created new army to cover previous loses but robb seem ok with  a army that is getting smaller battle by battle  even with the riverlands army suporting him.

[I Don't Shagwell]

Winter is coming...

 

edit.

in all seriousness though. I think many reasons and every one of them comes to fruition.

ironborn

wildings

treachery

[The Golden Wolf]

4 minutes ago, I Don't Shagwell said:

Winter is coming...

this...literally. The North is constantly preparing for Winter. taking more men would mean that even more of the harvest would be ruined which is something the North cannot afford. When Robb marches it is not to wage a lengthy campaign against the Lannisters but to show force, win a few battles, help the Riverlands, and rescue his father and sisters. If his family had been returned unharmed The North would have went back home and prepared for winter. 

Joffery killing Ned ruined any hope of a quick campaign

[hodorisfaclessman]

He wants to strike hard and fast so takes all he can as quickly as he can 

[Chris Mormont]

There isn't enough men to form another army.  The North is not very populated and you will still need men to bring in the harvest, defend their lands etc.  This is why Bolton is able to take over unopposed, he was very careful with his men during Robb's war. 

[The Young Maester]

Aye, the North is underpopulated when compared to the vast amount of land they rule, but you forget the North is the largest kingdom and can fit all the rest of kingdoms inside it. George RR Martin himself stated that both the North and the Vale can raise an army of 45k at full strength (likely including old men and green boys.) I reckon 15k of this 45k are old and green due to the fact that King Torrhen Stark marched south with an army of 30k, and seeing how Westeros has just had the longest summer in recorded history I reckon Robb had another 10-11k strong aged men available in the North. 

You forget that Westeros has been around for 8,000 years (after the long night) which means that the population has no doubt been increasing slowly but slowly and with the seven kingdoms united for 300 years for a good period of peace, this is another boost on population especially for the North as they have had king on the Iron Throne supplying/trading with the northern lords with food from the Riverlands and the reach. Remember before Aegon's conquest these southern kingdoms would never have established any sort of diplomatic communication with the North due to their worship of the old gods and that many that live south of the neck believe them to be savages. To further add the north used to be very very isolationist before Aegon's conquest. 

Each kingdom is able to raise around 2% of their current population, why I say this? because for example, the UK has a population of about 65 million in which if the nation were to decide to call for all able men this would be 2% of the population (2% of 65 million= 1.3 million). This number is accurate because during ww1/ww2 the British Empire was able to raise armies around this figure from just their sole islands of Great Britain.

Now going into the Westerosi population-

North- 2% of the 2 million = 40k 

Vale- 2% of the 2 million = 40k

Riverlands- 2% of the 3 million = 60k (Tywin devasted the Riverlands therefore the Tullys cant raise these numbers)

Westerlands- 2% of the 2.5 million = 50k

Reach- 2% of the 5 million = 100k

Stormlands- 2% of the 1.25 million = 25k

Dorne- 2% of the 750k = 15k

Iron Islands- 2% of the 750k = 15k 

 

[Leonardo]

It has much more to do with food. The population of the North is probably in the top half of the seven kingdoms pop. based on size, size of far northern vassals like Karstark and Umber, and arable land. A northern army is almost impossible to feed based on its size and logistics... 

[The Young Maester]

6 hours ago, Leonardo said:

It has much more to do with food. The population of the North is probably in the top half of the seven kingdoms pop. based on size, size of far northern vassals like Karstark and Umber, and arable land. A northern army is almost impossible to feed based on its size and logistics... 

For this reason is why Robb wishes to march south as soon as possible, he doesn't have much food to last long in the north. But once the army touches the south thats not an issue as they can supply themselves with the food of the landscape like every other army has done historically during wars. During medieval times an army would feed its self by looting and pillaging the enemy's lands, which is something Robb was doing in the westerlands , honourable or not it did not matter he had to feed his army.

When Robb invades the westerlands, he takes the crops and food from conquered parts of the westerlands. Same for Roose Bolton who is feeding his army by taking food from the local peasants and from the crownlander lands. Logistics is an issue for the north, but only when they are IN the North, once they march south they feed themselves with the aid of allies and by taking the food from the local lands. I also doubt the North has a supply line connected to Moat Cailin because the march through the bogs, and swamps would just not be worth it to establish a steady supply line.