I really do not understand the need to lash out enormous funds from already wonky economies to build aircraft carriers and sophisticated aircraft to fight what has become global asynchronous warfare. The US, the country with the most advanced weaponry, the largest air force and navy were unable to take out the rag tag Vietnamese fifty years ago and have not been able to put down the Afghans, the Al Qaeda or the IS over the last dozen years.
The US and the EU both try to justify the investment in conventional arms by hyping up fear of the Yellow Peril and Russian Bear. This is particularly true of the US which is unable to shed the cold war mind set and its glorification of the military. The people have become “wannabe” warriors and, in lieu of joining the armed forces, they kill each other in street battles armed with 300 million privately owned weapons. The US police, armed with assault weapons, have now become as feared as the criminals by the public.
What is needed to deal with threats such as the IS and other radical groups is investment in better Intelligence, Humint, not NSA/GCHQ gadgets, but assets on the ground infiltrating the radicals. The US armed bin Laden but didn’t suss out his motives until too late. They did not have an embassy in Iraq so no base for recruiting intelligence assets so they blundered into a disastrous war, the price for which the US and Europe are still paying. The West did not foresee the rise of IS and still have no idea of their numbers or how to fight them. Air strikes and aircraft carriers are certainly not going to be the answer, something even the military blockheads are now openly admitting.
As for domestic threats again what is needed is Intelligence, not conventional weapons. I think this is particularly true of the UK with the large number of disaffected UK Muslims fighting in Syria and Iraq. This could also pose a threat to the US by individuals but not, as the US war hawks contend, an organised attack on the mainland by the Islamic State.
The only need for large scale armies and conventional weaponry such as naval and air resources would be conflicts amongst large land based nation states such the US, Russia and China. However, even there the deciding factor would be nuclear ballistic weapons with armies needed only to do mopping up operations. The military mind has always been behind the curve.