Why are the Westerosi soldiers seen in small groups?

Question

There have been times in the show where we have seen soldiers, particularly Lannister soldiers, travelling in small groups through the Riverlands. One example of this is when Polliver and five other men were in an inn where they encountered the Hound and Arya. A more recent example comes from the most recent episode, wherein:

Arya encounters a group of eight Lannister soldiers camping by a fire together.

I'm sure there are more examples but these are the only two that come to mind.

Polliver’s men in particular confuse me; they seem to be causing general havoc, which would have made sense before. But, at the time, the Riverlands were ruled by the Freys who were allies of the Lannisters.

As for the soldiers in season 7 episode 1 we are given some explanation:

they tell Arya that they are part of the army who have been sent to deal with the 'trouble' that the Freys are having.

So why are these soldiers not marching in bulk? It seems to lead to a higher chance of desertion, separation or men being picked off by the Brotherhood. What reason could there possibly be for soldiers to be travelling in such small groups?

Answer 1

There are two base assumptions:

1. Lannister Army has reached their destination and is operating in their deployment area.
2. Lannister Army still hasn't reached their designated area and is en march.

Assumption #1

If we assume that Lannister have reached their destination, small parties should not be surprising.

Their mission is maintain the peace and stop the political situation from devolving into general mayhem. The said mayhem is caused by resistance fighters, bandits and Broken men.

These offenders are generally found in smaller groups and retreat when they see a larger Army coming their way. Not to mention, Larger armies are easier to track than smaller parties.

That's why small patrols have a greater chance of success than moving the entire army all the time. It is also cheaper as small parties can easily fend for themselves whereas armies require upkeep.

Also, there's a chance they might be foragers but foraging is mostly done in wartime when resources are scarce. Also they don't have carts to haul their booty so I doubt they are foragers.

Assumption #2

If the Lannister Army is still on their way to their deployment area, it is customary to surround a marching army with scouts and outriders to get an advanced warning of an ambush. No smart general moves without spreading his eyes and ears far and wide.

It is possible that Arya actually met scouts rather than the main body. The men are too few to be rear-guard or vanguard of the Army so most likely they are a scout unit.

Sure there is risk of desertion in these scenarios but that risk is present all the time. And Lannister Army may be tired but they have won the war. So their morale can't possibly be that bad. Conventional wisdom dictates that their commanders should send out small parties out both in march and when they reach their area of responsibility. The possibility of notorious outlaws such as tBwoB is very strong as well but that's their mission isn't it? Find out outlaws, root them out, if outnumbered, return back to the base and report your findings.

Case of Polliver's men

It is a saying that there's a beast in every man which comes out when you thrust a sword in its hands. That particular band is sworn to notorious Ser Gregor Clegane. They seem to be doing what some soldiers like to do i.e. rape and plunder. There's more for you to rape and more for you to plunder if your competitors aka comrades are less. Who's going to oppose them anyways for them to move in large parties? All their enemies are defeated. They could go out on any pretext such as foraging or scouting and fill their pockets. The Local lords are unlikely to resist to King's men.

Answer 2

They tell Arya that they are part of the Lannister army who have been sent to deal with the 'trouble' that the Freys are having

The simple addition of a comma could somewhat change the meaning:

They tell Arya that they are part of the Lannister army, who have been sent to deal with the 'trouble' that the Freys are having

In this case "who" could refer to "part of the Lannister army" rather than "the Lannister army".
In other words, not the entire army was sent to the Riverlands. They are normally part of the Lannister army, but they (not the entire army) have been sent to the Riverlands on a mission.

It would still be weird to only send 8 men in total, though.

However, as they are sent to the Riverlands because of the Frey murders, they may be investigating and patrolling the area, looking for insurgents. For that reason alone, their larger group could have split up on approach to the Twins, in order to maximize the chances that they encounter potential rebels who are hiding out in the forest.

They are also all relatively young men, which may hint that they are not the core of the regiment that was sent; and are maybe on their way to reinforce the Lannister presence that is already on their way to the Twins.

Answer 3

Without knowing the sizes of their operation let's assume a legion of 1000 soldiers are conducting operations on the front lines between hostile nations.

The bulk of the legion would be set up in camp at a secure operating base which small sorties on various missions would disembark from. If 15 percent of the legion are required to manage and defend the base 850 men of the legion would conduct operations.

Of 850 men at any given time one third would be prepping for missions one third would be on recovery operations and the remaining third would be on missions.

So at any given time 280 men would be off base doing what lanisters do. If the missions they are on last a week they would most likely sustain themselves by foraging more so than rations pre packed.

So 10 men in 28 teams would have an easier more effective time foraging if dispersed, also would be able to cover more ground, patrol more roads, set up more check points observe and raid more villages and guard more river crossings if split up.

Small groups operate during sustained operations large groups fight major battles. Until two major armies meet on a battle field the armies would either be massed in camps or out on small sorties. What you saw in season 7 episode 1 was a small group on a patrol. I would bet their main camp is several hours walk away and there would be several small groups within close proximity of them.

Answer 4

We are talking about a medieval army here. As such, we should assume that they are foraging to sustain themselves. Sure it makes them vulnerable, but you need food and fodder. If you know an enemy is within reach (a few hours), you concentrate your forces. But not before, that will simply drain the regions food stock.