The strategic view ought to have begun with the demography on the one hand and the eternal realities of of UK geography and geology.
As an island chain off the coast of Europe, effectively dominating access via the Channel, and the North Sea. The UK has no choice but to be concerned with maritime matters. As surely as it must nearby states which control neighbouring coastlines.
As a state who's population exceeds it's capacity to feed from it's domestic agriculture, imports in bulk by ship from wherever imposes a life or death demand for maritime security of trade along the routes that food travels.
That ultimately requires military force to create that security.
This food has to be paid for, domestic economics must earn acceptable foreign capital to buy those imports. Foreigner's must want what is made in the UK.
All import is subject to threat of restrictions, from capacity to availability to political interference to financial constraints.
Each import is a weakness.
Demographically, the UK population hit a low of birthrate in 1972-74 and this means by the early 1990's that cadre is entering the workforce and is the available pool of new recruits to UK Armed Forces.
Arguably a contraction in population matched with increasing agricultural productivity eases the import burden, eases pressure on 'housing'.
Which includes:-
sewage treatment
water provision
electrical power supply
healthcare
education,
wealthfare,
transportation,
emergency services,
government services,
legal services,
financial services etc
and on and on and on...
housing is not just housing.
Increasing productivity and efficiency decreases the pressure to import labour.....
if the educational system is working well...........
a failure to educate to the needs of the economy results in increasing pressure to import people with those skills imposing assimilation and integration costs.
Importing people always runs the risk of importing foreign disputes and runs risks concerning divided loyalties.
The offset of technologies, and improving exchange ratios assist in offsetting a decline in personnel numbers in the Armed Forces.
Historically the need for large standing armies ran counter to the more pressing need to crew a navy sufficient to control access to the UK. It's hard to win a war on UK soil if you cannot get your army across the seas.
In the world of Atomic weapons, and ballistic missiles, the UK is too close to potential launch sites in the Soviet Union. Flight times impose a very short warning period and decision time is measured in minutes.
To this end defence would have to be fully automated and this runs risks of accidental use.
The best option would be to cite such interceptors closer to the threat.....In Europe or at sea.
Logically threats from further away might permit a more US style decision system. Giving humans time to choose. Such as China or Iran.
The posture of retaliation is sustained by a domestic sourced system. Every foreign element bar certain critical supplies (uranium, certain rare metals and minerals) is sourced to reduced costs.
There is a strong argument that UK nuclear weapons numbers be too low. Even prior to the end of the Cold War.
Everything that is made in the UK, from UK sourced resources and priced in domestic currency sustains UK Independence and any such exported is of net benefit to UK finances.
For every imported element, increases exposure to international politics and exposes the UK economy to external pressures. Imposing greater need for foreign involvements and often tangentially to UK objectives.
In essence UK support of involvement buys the UK support from other states to secure UK objectives.
The UK sits on reserves of oil, gas, coal, iron, tin, salt, chalk and certain phosphate bearing rocks.
Agriculturally the UK climate results in a good environment for grases, both for human consumption and to raise cattle, sheep and pigs. The quality of the meat has been the result of the temperate high water content grasses and vegetables.
The seas around are particularly good for fishing, though overfishing has caused problems. This sector imposes a need to establish 'good' relationships with other states sharing these seas.
In virtually every element of this, from the UK perspective the Sea and the Navy loom large.
The Army in deployed form is essentially a bargaining chip to buy influence.
It's military capability is secondary to the perception of it's utility to foreign states. If they think it of value in assistance to their objectives, it buys the UK influence in the corridors of power in those states. As surely as it's potential threat.