Russia announced a nuclear-tipped torpedo. A bit gloaty about the ability to inundat coastal cities with radioactive tsunamis. They've been beefing up their nuclear arsenal for a while now, whether the claims of hypersonic nukes or ramped up MIRVs.
The PRC's been doing the same--it's never been covered by an arms control treaty, mind you--as well as hardening military installations and making it possible to quickly relocate nuclear missiles like Saddam Hussein could relocated SCUDs. Some of the hardware they showcased at their "we won WWII" in order to rewrite the popular understanding of WWII's land-based Asia front were new nukes.
We've "tested" our weapons using models but really haven't added to them because, well, it would be irresponsible to try to maintain some sort of mutually assured destruction. They've built based on models. But since we don't have much in the pipeline if we want to saber rattle with anything like the same degree of malicious glee and triumphalism we're left with actual testing. (Then there's the ever loverly PRNK and its shifting alliances with the PRC and Russia or both, mixed in with pacifist Iranian support.)
"Golden Dome" rattled both Putin and Xi and the PRNK and they decried it as being undemocratic or whatever bit of palaver it was because it would shortchange the peace-loving protectors of the vulnerable and good and just against the militaristic land-grabbing genocidal evil Americans.
Note that both programs started before Trump 1.0, and not in anticipation of his winning in 2016. Even letting one of the longer-standing arms control treaties with Russia lapse was anticlimactic because we knew that they were violating it but in a plausibly deniable manner, and in too short a time after it lapsed suddenly fully formed new nuclear weapons were announced. (With the possibility that those on parade were just gutless mockups, which begs the question as to whether the real thing actually existed and in what state of development).
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