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Caesar Howitzer a good drink for a hangover
When the war is over and if Ukraine wins do they give back any weapons or vehicles they were given? >

I believe a lot of countries are using the aid to Ukraine also as a way to offload dated or overstocked equipment. Essentially, the donation to Ukraine is a good excuse to replace them with newer systems.
For example, Germany is in the process of replacing its Marders with a new IFV called the Puma. Hence why they are willing to donate the Marders. 
Similarly, the French last year were looking to update the Caesar platform. Instead of retrofitting the existing systems, they are now probably donating (most of) them to Ukraine and just ordering the upgraded version new.
As such, I wouldn’t expect any country to ask for its donated systems back. They will be worn out and already replaced. Doesn’t really make sense to keep a stockpile of worn and outdated stuff. >

Or as advertisement. In the case of the caesar, I seem to recall France getting 2 new deals on it a few months after sending the first batch to Ukraine.