Why there likely won't be a negotiated peace to end the war in Ukraine
A frozen conflict remains the most likely outcome
The Ukraine war has been at a stalemate for more than a year at this point, with the last major territorial change being the Ukrainian recapture of Kherson in November 2022. Trump, the likely winner of the 2024 US presidential election, has promised to end the war soon after assuming the office again, presumably through direct negotiation with Russia, and Putin has explicitly called for a negotiated end to the conflict.
However, the positions of the Russian and the Western/Ukrainian sides of the conflict are simply irreconcilable. A foundational pillar of the post-WW2 world order is that countries are not allowed to invade other countries for the purpose of annexing their territory. Upending this principle is likely to have wider consequences for world peace, and is simply unacceptable to the Western world, especially Europe which sees the non-acceptance of wars of conquest as foundational for European peace. A Russian withdrawal from most or all of Ukraine is thus a non-negotiable requirement for normalization of relations with Russia for most European countries.
On the other hand, Putin has made it clear that he has no desire to give up the territories he has conquered in Ukraine. 4 Ukrainian oblasts in addition to Crimea have been formally annexed, and the inhabitants of the conquered territories granted Russian citizenship. Putin giving up these territories would be an extraordinary show of weakness, and would severely weaken his position as leader of Russia. For Putin, recognition of these territorial changes is thus a non-negotiable requirement of normalizing relations with the West.
It is thus extremely unlikely that there is any negotiated peace that will be acceptable to both Russia and the majority of Western countries. Regardless of what Ukraine, the US and Russia may negotiate, the vast majority of Western countries are likely to maintain non-recognition of Russian annexations and severe sanctions on the Russian economy. This severely limits the incentive for the Ukrainians and the Russians to engage in good faith peace negotiations.
On the Ukrainian side, the likely continued backing of most of the Western world makes a negotiated peace acceptable to Russia very difficult politically. The Ukrainian constitution requires a referendum to be passed by a majority vote in order for any diminishment of Ukrainian sovereignty to occur. This would be a very hard sell to the Ukrainian electorate, when most of the Western world will remain steadfast in its support of Ukraine and its territorial claims.
There are some of the most severe sanctions that the US presidency could likely end unilaterally, such as the Russian exclusion from the Swift system. However, the US establishment, which has strong representation in both houses of congress, maintains the same basic position as the Europeans when it comes to the acceptability of wars of conquest. Their position is strong enough that they are likely to have a veto proof majority in both houses of Congress for legislatively enshrining most sanctions on Russia and the non-recognition of Russian territorial conquests should it seem likely that the presidency would act alone in these areas. This significantly complicates any attempt on the part of a future Trump presidency to negotiate an end to the war.
How is the Ukrainian war likely to end then? There will be no negotiated peace, although a formal ceasefire seems somewhat likely. The conflict and actual lines of control will simply freeze in place with no formal peace treaty. The Russian appetite for a full conquest of Ukraine, if it ever existed, seems to have long evaporated. Once Russia has conquered sufficient territory to be satisfied, likely to entail a full conquest of Donbass and maintenance of the land bridge to Crimea, Russian forces will dig in and focus on defending their acquired territories, as they already have to a significant extent. This will make Ukrainian counter-attacks increasingly futile. At that point, with no territorial changes over a longer period of time, and no prospect for a succesful Ukrainian counter-offensive, fighting is likely to more or less end, even in the absence of a negotiated ceasefire.
What then will be the outcome of the conflict? Russia will remain isolated from the West, with its economy significantly hampered by the continued sanctions. Russia is likely to become increasingly dependent on China for both its economy and security. China’s continued support for Russia is likely to be a sticking point in relations between the West and China. Not having full control over its territory is unlikely to be a significant barrier to Ukrainian EU membership, as the example of Cyprus shows. Ukraine is thus likely to become a member. On the other hand, NATO membership is extremely unlikely in the absence of a formal peace treaty with Russian, given that simply the continued presence of Russian troops in internationally recognized Ukrainian territory would constitute ample grounds for invoking article 5.