Nice Quora writeup by user Carter Moore here, quoted in full below. I have a thing for imaginative well-researched answers like this:
So you’ve decided to take on a modern and experienced professional fighting force of some 116,000 personnel, but you’re unsure where to begin. That’s perfectly reasonable. Defeating one of the world’s most highly regarded military organizations is a pretty daunting task.
Many people have tried to defeat the British Army over the course of centuries, and most of them have failed. But hopefully with this advice, you and your victorious army (you do have an army, right?) will be knocking on the Queen’s door in no time.
The primary issue with attacking the British Army is that they’re really, really good at defending themselves from aggressors or would-be aggressors who play by the rules, make themselves known, and fight in the open. You will have to rely on the element of surprise for your attack to have maximum chances of success. Keeping that in mind:
Step 1: Set up your army in Norway
With a few exceptions, England hasn’t had to anticipate an invasion from the direction of Norway in the last 1,000 years; so it’s unlikely that they will be expecting your army to come from there. The Norwegian fjords offer you plenty of opportunities to shield your army from detection until they’re ready to launch.
I estimate that you’ll need a well-trained fighting force of some 50,000, to include an air component, in order to reasonably assure numerical advantage in your attack. You might notice that this is a smaller number than the total size of the British Army I noted earlier, but keep reading. I would also highly recommend you include an air component to fend off the Royal Air Force.
Step 2: Hijack a Vanguard-class ballistic missile submarine
Of all the contingency plans that might exist within the Ministry of Defence, I’m going to go out on a limb and doubt that they have one entitled, “The Bastards Use Our Own Ships Against Us.”
Nobody has ever successfully (or, to my knowledge, unsuccessfully) attempted to take command of a nuclear submarine, which means they might not expect your attack to begin here. Given that the Royal Navy based its submarine fleet in Scotland of all places, it seems probable that they won’t notice one of them missing for at least a few hours.
How you choose to defeat the Royal Marines guarding the base and take command of the vessel is entirely up to you, but a full frontal attack is not advised (see: British are good at defending themselves in open warfare). As has been discussed elsewhere, it’s not likely that those guarding the submarine fleet have been trained to anticipate an assault that relies primarily on slingshots, so I would recommend you explore this possibility in detail. I also have it on good authority that they no longer train to fight against swords and longbows.
Alternately, if you’re the patient type, enlist in the Royal Navy and diligently work your way up the ranks until you’re in legitimate command of one of Britain’s nuclear-armed vessels, and then turn “traitor.” The difficulty here is that most – if not all – of your crew might interfere with your plans to attack their country, so you should have loyalists in key positions to assist with putting down the mutiny.
Step 3: Eliminate most of the British Army
You might be disappointed to learn that your new submarine contains a mere 40 W76-type nuclear warheads across a paltry eight missiles, but this will be more than sufficient to eliminate most of the Army’s fighting strength. Most of the Army’s garrisons are concentrated in just five major military installations, with satellite garrisons spread across 30 counties. As such, your new-found nuclear capability should be sufficient to destroy most of the Army’s headquarters units and the majority of its personnel and equipment.
However, I’m reasonably confident that the UK has not targeted its nuclear warheads against itself, and I’m not intimately familiar with the retargeting process. There should be an instruction manual onboard the submarine to help you through this process.
Your first salvo of warheads should be set to detonate approximately 100 kilometers above Great Britain in order to maximize the electromagnetic pulse effects of the weapons. This will help disrupt or destroy any national power or communications systems that are likely to survive the secondary wave of attacks (again, owing to the small yields of the warheads you’re carrying).
Because of the small yield of the weapons, you will need multiple detonations to maximize the EMP effects across the country; and due to the orientation of the Earth’s magnetic field in the Northern Hemisphere, you will be detonating the devices approximately 200 kilometers to the north of your intended targets. I recommend an attack pattern (intended target) of:
- Coningsby (London)
- Bewerly (Birmingham)
- Wark (Manchester)
- Nairn (Edinburgh/Glasgow)
- Bunessan (Belfast)
Here’s where having your forces tucked away in the Norwegian fjords has an added benefit: By being several hundred kilometers to the northeast of the EMP bursts, they’re in a better position to be shielded from EMP than if they were arrayed along the English Channel. The London-intended high altitude burst alone could affect sensitive systems as far away as Germany.
Very shortly after the EMP attack, your salvo of warheads set for low-altitude detonation ought to reach their targets. Not only will the use of airbursts allow you to maximize the destructive potential of the nuclear weapons, but they will limit any fallout to the immediate area of destruction (being too high to pick up and disperse radioactive debris into the atmosphere). As such, the nuclear attack should not result in much obstruction for your invading forces. Your absolute priority targets should be:
- Ministry of Defence Headquarters at Whitehall
- Aldershot Garrison
- Bulford Camp
- Catterick Garrison
- Colchester Garrison
- Tidworth Camp
Bare minimum. Note the lack of bases along the eastern coast, ie, facing Norway.
Side note: The detonation over Whitehall will, unfortunately, obliterate the Queen’s door (and all persons and property within many square kilometers); so contrary to the introduction, it is not advised that you attempt to go knock on it to declare your victory following the successful implementation of this guide.
Keeping in mind the potential threat from the Royal Air Force in supporting the remnants of the Army in repelling your invasion, I recommend you consider exchanging the destruction of low-priority garrisons (eg, primarily training centers) in exchange for air stations High Wycombe, Coningsby, and Lossiemouth. You can adjust the number of targets as you see fit, but keep in mind that the bulk of your nuclear attack should be focused against the Army’s capabilities.
A very crude examination of an attack on the Army’s garrisons with 35 100 kiloton nuclear weapons comes up with some two million dead and 4,600 square kilometers of destroyed land (three percent of the UK’s people and two percent of its land area). This brings us to the next simple step.
Step 4: Evade/Attack the Royal Navy
By now, the Navy will have noticed that you’ve taken their submarine and used it to kill several million people, and this will make them unhappy.
Your personal best bet, frankly, is to beach the submarine somewhere along the English coast and get as far away from it as possible before reestablishing communications with your army-in-waiting.
It’s not cowardice if you live to rule again.
Your army’s best bet, however, would be for you to gallantly engage the Royal Navy with whatever torpedoes you have available in order to distract them from your invasion force. If you choose this route, though, be advised that the likelihood of your personal survival to see the full destruction of the British Army cannot be guaranteed.
Step 5: Taunt the Army a Second Time – Invade England
Given the chaos that’s sure to reign in the wake of your nuclear attack, your army should not have much trouble establishing a beachhead at a location of your choosing. Your presence should enrage the surviving Army – which I estimate to be down to 20 to 30 percent of its full strength, most of which should now consist of Reservists, who are not based at the now-flattened garrisons – and goad them into attacking.
It is not advised that you wait for the Army to be fully organized, however, and might instead choose to attack their components while they are detached from the main body. Your success will depend on the capabilities of your own armed forces.
Once you’ve mopped up the stragglers, you should take a brief minute to congratulate yourself for successfully defeating the British Army, and then prepare to defend yourself against the might of NATO’s counterattack.
To accomplish this, please refer to my guide, How to Surrender in 1 Easy Step.