Another Arms Race? Really? Do We Never Learn?

If one side (person, family, city, nation, alliance) has a weapon and acts like they might kill another side, then the other side has to respond. There is no limit in the effort to survive.

Ronald Reagan said he would give the Soviet Union technological plans to build perfect defenses, so they wouldn't have to be afraid of "The West". They declined, but now they have their own home-made defenses which are very good. Why isn't this sufficient?

What if both sides have sufficient defenses, but one side chooses to act in small acts of micro-terrorism which are difficult to assign to them. How do you limit continual bad behavior by one side?

It's natural that people who once thought "more bigger better" was always the answer to this question. But, isn't the greater security of each side more important? Let's not ruin a security balance wherein both sides are free from constant worry about their existence. Let's find the appropriate solution, the proportionate effective response.

http://www.businessinsider.com/russia-defenses-stop-us-air-force-artillery-upgrades-2018-3

http://thehill.com/homenews/administration/380923-trump-to-putin-if-you-want-to-have-an-arms-race-we-can-do-that-but

This worries me. It may be only because our current president (Trump) has a desire to lead a war. He has even said he likes war. But, for now this is what we must notice and oppose.