Question about promotion of enlisted by other forces

Can officers in one country’s armed forces promote an enlisted person in another country’s armed forces?

Consider the following scenarios:

An American force in Afghanistan, commanded by an American officer, have a British officer (field, not staff) with them. They come under fire and the American officer is killed, as are the sergeants. The British officer takes command and needs a sergeant, so on the spot he promotes someone.

A large group of American and British POWs are in a German POW camp in WW2. There are no Allied officers, but numerous sergeants of the same rank. Can the German commandant promote one of the sergeants to Sergeant-Major?

On a related issue, in WW1 and WW2, were recommendations for medals for those in captivity passed across lines (likely via the Red Cross) and honoured and presented?

No, but he can probably say: “You! Take command of your squad!” and that will be that. He doesn’t need to actually promote someone to get the job done - if he’s in charge, he can delegate whatever he wants to whoever he wants. You don’t need to outrank someone to give him orders

Afterwards, if his own chain of command sees he did a good job, a promotion may be in order.

Yes, a New Zealander recieved a VC on the recommedation of a german U-boat commander.