When judging the effect of the recently delivered HIMARS are having on the battlefield remember this; both the Ukrainians and the relatively few Russians that can speak freely are saying the same thing - they're devastating and the Russian military simply has no counter for them.$1:
They're also saying that relatively sophisticated Russian air defence systems like the S300 and the S400 that "should" be able to intercept HIMARS rockets (on paper) cannot.
And they're saying that the Russians have suffered significant losses in move men and materiel. And don't underestimate the effect on morale of previously safe areas now being incredibly dangerous, subject to an unstoppable HIMARS attack at any time.
This is what the Ukrainians have achieved with between 4-6 systems.
They're getting a minimum of 6 more HIMARS and 9 M270 MLRS systems (which has twice the firepower of each HIMARS system) over the next month. That's a huge amount of firepower.
And let's think about the strategic picture...
This kind of incredibly accurate, virtually unstoppable long range firepower makes a Russian strategy of "digging in and annexing" occupied territory virtually impossible. It fundamentally changes the strategic calculation.
Tomorrow Russia will take Nord Stream 1 offlineThere will be a major potential for escalation of the geopolitical and energy crisis
So here's a thread on why not to panic now, when you might want to, and just what on earth is EU Regulation 2017/1938
Ukrainian GMLRS strikes are sure working down the Russian target array checklistAnd the Russian military is complaining neither S-300 nor S-400 anti-missile radars are even seeing the inbound GMLRS strike.