Russia may not like a war but Russia needs resources since it wants to be the only store in neighborhood, and unfortunately, Ukraine does have resources. War was not expected outcome of the initial scare tactic but here we are.
However both UK and USA are failed states, their extreme capitalism put too much of their population in poverty and without immigration they simply fall on their own weight.
As before they NEED a war to overthought the table and start over. And they have actually created that, it's not a secret, it's written black on white if only you read their publications from RAND to G8. They use a slightly strange vocabulary but it's clear what they state. They call themselves "the international community" or "the civilized world" but it's clear they just mean their fragmented former colonies. The same have happened in the recent past with the Korea war, as it happened their former colonies start to decide it's time to detach a bit, like SK an Japan themselves https://asiatimes.com/2022/08/japan-korea-defy-us-with-big-r... and even New Zealand https://thediplomat.com/2022/07/new-zealand-will-not-join-th... Australia itself suffering the submarines scam the UK and USA essentially have imposed to them ditching modern but limited French subs to exactly nothing since for a decade at least that's what they'll get (less than nothing since they have payed compensation for the late choice) start to falter undecided witch side to take. Only high treason neoliberal government in the EU keep the USA/UK side against their own Citizens interests.
Some in US and UK have already understood that their war is lost and they menace them to go nuclear in that case, see https://www.independent.co.uk/news/uk/politics/liz-truss-nuc... and https://www.dailymail.co.uk/news/article-11110441/Henry-Kiss... but the rest of the world, the BRICS start to unite knowing that it's freedom or death for them. They have all tested the "freedom" neoliberal nazi means, to a point in eastern Europe many would welcome back Soviet Union...
The above are NOT political or ideological positions but simply facts anyone observing with honesty no matter the personal political position can't avoid to see.
Long story short: yes, is Russia that have crossed the border, but no, it's not it who start the war in reality.
Try a small game, put PR and the emotion they push aside: who need a war today? If you are honest you have to admit that the most in need of a war are UK first, USA second. UK need a war outside to avoid a civil war inside. Having essentially lost their "empire" status they are simply unable to live anymore. A war would compact people and if won give resource of the looser. USA need a war for similar reasons, mitigated by the fact that USA can actually live on it's own, even alone, "only" correcting it's crazy economy. Not easy at all, but technically possible, so practically when crisis really bite.
China do not need, but like, a war. They have a hyper big food issue, they need to conquer south America to eat. To do so they need to overpower the USA. To do so they need Russia's tech and natural resources, something Russia, a China's historic enemy, do not like that much to share to such a big & powerful giant.
Russia do not like a war at all. It's something that impose agreements with China, imbalanced. EU similarly do not need a war. It simply destroy EU itself due to the lack of natural resources.
So the plan is? Well. USA declare it essentially in the far 2004: https://www.dni.gov/files/documents/Global%20Trends_Mapping%... oh, they are formally just acritical prediction from the intelligence to the politicians. But sounds really accurate. In more modern terms: https://www.rand.org/content/dam/rand/pubs/research_briefs/R...
A bottomline: saying that UK and USA need a war means their oppressive ruling classes need it, of course NOT the people, unfortunately as most people in the world those who do need the opposite of their ruling class are the last to understand they are fighting for their own enemy that's not those on the opposite front, but those who march at their head.