Let us imagine that for some reason France has decided to invade the Island of Jersey (a Crown Dependency) with 100 soldiers who are now stationed on the island.
The standard operating figure for an infantry assault is 3:1 (One to cover, one to kill and one as a spare). So Britain organises an assault group of 300 infantrymen. These 300 men have to be transported on the amphibious carrier HMS Albion. HMS Albion requires a crew of 325 sailors. Of course, we cannot just send infantry, embarked with them are one artillery gun (6 men), a fire control team (2 men), an engineer platoon (30 men), a logistics support unit (250 men), a mechanical team (12 men) and a field hospital (300 men).
Unfortunately HMS Albion now has her full capacity of 800 embarked troops. This means that her sister ship - HMS Bulwark (also with a complement of 325 sailors) has to be mobilised. The assault troops require intelligence so a intelligence cell must be embarked (12 men), a Human Resources unit must be in place (20 men), a section of military police must be present (10 men), a signals squadron (150 men) and finally (for the army at least) the battlegroup padre.
Of course, HMS Bulwark and HMS Albion cannot sail alone. They must be part of a fleet of ships in support. To this end the following ships are mobilised: HMS Daring (195 sailors), HMS Dauntless (195 sailors), HMS Argyll (185 sailors), HMS Iron Duke (185 sailors), HMS Kent (185 sailors), HMS Cornwall (250 sailors), HMS Astute (98 sailors), HMS Ledbury (45 sailors) and HMS Bangor (45 sailors). These ships will need support ships to refuel and re-arm them and so the support ships RFA Wave Knight (72 sailors), RFA Fort Austin (195 sailors), RFA Fort George (288 sailors) and RFA Diligence (185 sailors) are mobilised.
It need not be said that these ships will require air cover. Thus HMS Illustrious (1051 sailors and airmen) is mobilised. Of course, this means that there must be at least one Joint Tactical Air Control team (4 men). Finally the task force must have helicopter support in the form of HMS Ocean (465 sailors) who can move the troops (via helicopter) to where they need to be and can carry some extra supplies.
So, in order to dislodge 100 Frenchmen for the Island of Jersey we would require about 5386 troops - and I didn't include the support troops back in the UK. Unfortunately, people don't tend to invade with a mere 100 men. In the Falklands I believe the total Argentine presence was something around the 13,000 mark. As you no doubt see, the numbers quickly stack up.
I hope at the very least to have given some of you an appreciation of how many people are required to undertake even small military operations; so let’s not have any more of this stupid, "the army is too big" nonsense.