Unless there’s a war going on, developing new or improved military equipment or weapons is delayed by bureaucrats more concerned about avoiding mistakes than getting the job done. This leads to lots of delays. The Ukraine War has changed that for NATO nations and Russia. While the Ukrainians develop a lot of their own weapons, and always have, they need more and that is what their NATO allies are supplying. With a war going on in Ukraine, it’s easier for the NATO defense procurement officials to say yes. With their nation under attack, Ukrainian developers are coming up with new weapons and equipment as well as upgrades for items they have received from NATO nations. Ukraine can put new or improved systems to the test quickly. Sometimes the Ukrainians don’t tell their NATO allies about new items used or produced in Ukraine because the NATO countries are more likely to publicize that. The Ukrainians are more discreet, realizing that what the Russians don’t know about will hurt them more. At the start of the war the Russians underestimated Ukrainian weapons and military equipment and the Ukrainians’ ability to use it effectively. This continues to supply the Russians with unexpected and unpleasant surprises.
NATO countries still supply most of the weapons and ammunition the Ukrainians need and for that they receive a lot of feedback on what works and what doesn’t. This has been valuable to NATO nations, which are now producing more effective weapons and military equipment for Ukrainian forces as well as for NATO to use in some future conflict. NATO countries may not have troops in Ukraine but there are a lot of technical specialists examining captured Russian weapons and equipment as well as how well, or not so well, donated NATO material is performing. Some of these NATO specialists are military, often described as diplomatic personnel, and are there to speed up the assessments. Sometimes NATO nations will find Ukrainian assessments incredible and hard to believe. By having NATO nation experts on hand, the Ukrainian assessments can be confirmed.
Sometimes Ukrainians will go to neighboring Poland to report on what is working, what is not and what is needed to improve the situation. NATO also provides training for Ukrainian troops in Poland before the Ukrainians and the new NATO weapons or equipment return to Ukraine to be used against the Russians. As much as Russia would like to attack, with missiles, these training activities in Poland, they don’t because that would trigger the mutual defense clause of the NATO agreement. If you attack one NATO member, all the other NATO countries consider themselves under attack and fight back. It's bad enough that NATO is supplying Ukraine with weapons and equipment. Being at war with the NATO alliance is a far more dangerous proposition for Russia.