Difference between the Marines and Army.



Firstly, I am British, so I have 0 clue on how the US armed forces work.

My limited knowledge of the system tells me that marines and the army perform the same task, which is the primary land based attack force.

So what exactly is the difference between the 2 and how does the US decide which force to mobilise and when?

In: Other

It’s really important to note that in the 21st century the US military has separate branches of service but ultimately they tend to operate under a joint/unified structure (working together as one unit when possible and necessary and feasible to execute missions rather than doing things individually, though as you can imagine the Navy with its ships is still responsible for mostly doing things at sea while the Army is still responsible for mostly doing things on land). At the peak of operations in Iraq and Afghanistan it was not uncommon to have people from all the branches deploying together in one location to support missions you might think are traditionally just “for the Army”.

The Marine Corps is one of those branches of service – it recruits, trains, equips and deploys its own forces. *But*, it falls under the overall umbrella of the Department of the Navy. It is postured around the world and on Navy vessels to deploy rapidly to any point in the world, establish a beachhead, establish a temporary basing point, and start blowing things up so other forces can come in and start making a more permanent presence. It’s oftentimes called the “tip of the spear”, since they’re known as being the “first ones to fight”.

The Army is its own branch of service and its own department (the Department of the Army). It also focuses a lot on ground operations, but it’s usually larger scale, longer term deployments meant to maintain that momentum and presence that the Navy and Marines established.

The Army is significantly bigger (more people and equipment) than the Marine Corps.

From my limited knowledge, the Army is basically the land-based attack force, the Navy is the sea-based attack force, and the Air Force is the air attack force. In case of war, these three attack forces would proceed to wage war in their respective domains (land, air, sea).

Carriers (and their escort ships, basically a carrier task force) can “project power”, basically you park a carrier off the coast and you “threaten” with it. Carriers can launch planes so they have their own naval-aviation mini-air-force, and they can also launch troops (the Marines). Basically, this is a smaller force that can do air, sea, and ground attacks, but for projecting power and, basically, diplomacy, rather than full out war.

So, TLDR, World War 3 = Army + Navy + Air Force, whereas reacting to some emergency situation somewhere (genocide, local war, etc.) = send a carrier task force with naval gunnery and missiles, naval-aviation, and marines.

Marines are a quick reaction small scale amphibious capable force and can be deployed anywhere in the world in 24 hours. Army is basically a large scale occupational ground force. As far as combat operations go, they have similar capabilities and missions although army typically has more resources available to them. Marines hitch rides on navy ships to places around the world and army typically flies in. If you need a force to assault a city and drive out enemy fighters you call the marines, if you need a force to maintain a long term hold on that city and repel attacks you call the army.

The majority of the differences are organizational – the Marines and the Army have their own hierarchy, they’re structured, organized, and outfitted differently, get their own budgets, etc.

But at a simple level of “what do these groups do in a conflict,” it’s the same as it’s historically been. The point of having a Navy (which Marines are technically structured under) is to control oceans and transport routes, and to quickly respond to threats. Marines are the units of the Navy that are meant to mobilize and respond quickly. So if you have an urgent crisis or need defense at some specific point, the Marines are the organization to use – they’re specialized in working in smaller units and quickly getting to a specific point and defending it.

An army, on the other hand, is a huge, slow-moving beast. The point of an army is to control a territory completely. So while it can’t mobilize as quickly as the Marines, it’s a larger operation that can provide more long-term support – heavy artillery, entrenched bases, and maintaining a presence for years.

The general idea is that if some spot is in trouble, you send Marines in first, because they’re built to take small groups, get to a place quickly and capture or hold it effectively. Then send the Army in to defend it – they’re more specialized in that way and they’re built to maintain that position or advance it for months or years, while the Marines are redeployed to the next mission. Obviously there’s an enormous amount of overlap between the organizations of the armed forces today, but that’s sort of the key strength of each organization.

The US Marines is a much smaller military branch then the US Army with only a fraction of the number of members. However they have much tougher requirements and train much harder. The concept is that the marines are the first ones into combat and work with limited resources and time. This means that they have to rely much more heavily on each individual marine and each marine have to do an effective job with the resources he have available. The army is expected to take longer to deploy and rely more on help from the navy and air force but when they deploy they have a lot of people and is a much more powerful force through share numbers and resources alone.

If you want some comparison to the British military the US Marines can be compared to the Special Air Service. However the scales are completely different as the entire US Marine Corps is a bit bigger then the entire British military.