When I was a teenager and the Cold War was at its height we were constantly hearing about the "arms race" between Russia and the USA. This battle for technological supremacy was closely related to the "space race" and the shock in the West when Russia was first to put a man into space was like an earthquake.
The arms race has never been exactly symmetrical. The initial technical problem - something that N Korea is rediscovering - was that nuclear warheads were too heavy to be carried by the rockets that both Russians and Americans had plundered from Nazi Germany at the end of the war. The Americans set about miniaturising the warheads. The Russians made bigger rockets. This, basically, was what gave them the edge in getting a man into space since humans cannot be miniaturised.
Eventually we arrived at MAD - "mutually assured destruction". The cost of war to both parties would be too devastating to make it ever worth trying. MAD may seem mad, evil even, but it did ensure there was no third world war. Various treaties were signed by the leading powers agreeing not to disturb this arrangement.
In this twenty-first century, however, the Americans have dropped out of these treaties and are intent upon creating a "shield" that would protect them from Russian missiles. This shield would consist of satellite tracking of incoming missiles and the firing of counter-missiles to shoot them down. At first sight this might seem sensible self-protection. One of the few things that President Trump has done that has attracted virtually no publicity or controversy has been to sign an order advancing this programme. As he signed it he made remarks to the effect that such weapons are a bad thing but as long as they exist the USA should have the best ones.
This has, however, set the arms race going again. Think about it. If the USA were in fact to become immune to attack by Russia (or anybody else) they would be in a position to impose themselves in any way they liked anywhere in the world. This is the kind of world domination ambition that has been shared by all the great empire builders in history. None of them has so far ever been able to totally pull it off however.
Secondly, there is virtually no such thing as a purely defensive system. A missile launcher can fire any number of warheads with any of a wide variety of targets. The official reason that China is protesting at the US putting its THAAD system into S Korea is that it can be used for espionage inside China, but one can be sure that they are also aware that a missile fired by THAAD could hit Beijing.
How has Russia responded? The Russians have said that they cannot afford to follow suit. Putin has no intention of developing a Russian shield. In any case it would be even more expensive for them as Russia is bigger. So what are they going to do? They are developing more powerful offensive weapons with the aim that if and when the American system ever becomes operational it will already be obsolete because the Russians will have some new weapon that can go through it. So it really is a race against the clock.
The arms race has gone on throughout history. Sometimes it advances rapidly, sometimes more slowly. The risks are huge. The cost astronomical. The whole thing certainly is crazy, but it seems we are somehow locked into it - a heartless machine in which we are at best cogs and at worst victims. People get used to almost anything. Somehow we have got used to the idea that we might all one day be incinerated. So much so that it rarely even gets into the news these days.