system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What does it mean if Russia leaves the 1987 nuclear treaty?
gpt
It means they'll start testing new missiles and nuclear systems. The other parties to the treaty (most importantly the US) will probably start too. 

If it happens, you'll probably start seeing an increase in military development projects from both sides, along with more sabre rattling. However, it won't go any further than that.