We are all members of the globe earth. Whether we like it or not it is a very, very interconnected world so what happens in other countries directly affect us and our strategic interests.
30% of our energy comes from abroad, the majority of industries raw materials and 50% of our food and to pay for these there we sell goods and services to countries all around the world. We have direct interests in making sure that this continues.
Individuals, communities and countries band together to protect their mutual interests. If we take the totally selfish view of the world (which more and more people in the West are doing) we end up with this:
They invaded far off countries and they got stronger, nothing to do with us.
They invaded neighbouring countries, nothing to do with us.
They invaded and conquered our country, nothing to do with us.
They killed all members of the old government and their officials, nothing to do with us.
They came for people in our town, nothing to do with us.
The took people from our street, nothing to do with us.
They came, arrested my neighbours, nothing to do with us.
Then they came for me and my family......
We in the West have major problems with our current weak willed, nth-degree equality (socialism) of everything politicians, who think all people are nice and like them. Well they are not, there are plenty of ruthless lying, cheating, thieving, murdering, power mad, bad people people out there that use this to get as far up the pile as possible and preferably right to the top so they are the countries next dictator. Our never had it so easy and good populations interests start and end at: The latest 50" TV, iPhone and iPad and all goods and services that by magic are in shops to buy. The latest 'entertainment' via TV, smartphone or cinema. A community is found by participating in a multi-player game and their only interest in military service is Call of Duty. Hardship is a Social cheque arriving a day late.
Whereas in Eastern Europe, Africa, Asia and South America from young childhood it is working the family smallholding, a productivity bonus, is successfully growing plenty of crops, so you eat, semi-starving if not, not every brother, sister, father, mother, uncle or aunt surviving through disease, tribal warfare and score settling. They are used to hardship. The Eastern European slavic nations thrive on it, life is cheap and easily replaced, -25degC outside, just get on with it. The softest thing about the average Ukrainian and Russian are their teeth.
Russia's annexation of Crimea show we are back to big eat small or weak power politics after 70 years of a world consensus and order. Like it or not, we are going to have to get used to fighting (directly or by proxy through our armed forces) to keep what we have got again or lose it. In all countries and communities, the most dangerous and disliked adversary that makes it close and personal for all, is the 5th column.