The coalition of the willing is not needed. If there is no peace to police there is no need. If there is an eventual ceasefire Putin will not accept UK troops in Ukraine.
Instead there is a bigger moral and political choice to be made. Ukraine wants many more weapons and ammunition. The US is wanting to supply less. Should European countries greatly increase their support for Ukraine and for a longer war? Should the UK do more?
Measured as a percentage of GDP the US and UK have led with gifts of military equipment. Germany has been the best of the major EU countries. France and Italy have been the laggards offering under a third of the US/UK levels.
Getting Ukraine to fight on alone means more deaths and destruction but could it bring victory? There is rightly no US/ UK wish to go to war with Russia.
There is a case to say as the EU has strong views on the Russian invasion and has land frontiers with Russia and Ukraine we should expect all these EU countries who have so far contributed little to pick up the challenge. France could lead it as her President makes plenty of warlike speeches.
The struggle is after all between Russia seeking to govern Ukraine after seizing it by violent invasion, and the EU governing Ukraine after helping a Ukraine government that supports EU membership .
The UK should step up defence spend but on home defence.Our needs are better defences against missile and drone attack, and an enhanced navy and airforce to protect our islands and trade routes.