Does the US Congress have to authorize non-combat deployments (e.g. of advisers and trainers) from the US armed forces to a foreign country?

Question

Back in 2020, the BBC wrote:

Turkey's parliament has passed a bill that will allow the government to deploy troops to Libya to intervene in the civil war.

Turkish lawmakers approved the bill on Thursday, with 325 in favour to 184 against.

In a phone call with Turkish President Recep Tayyip Erdogan, US President Donald Trump warned against "foreign interference" in Libya, the White House said.

On Friday, Greece's Prime Minister Kyriakos Mitsotakis, Israeli Prime Minister Benjamin Netanyahu and Cypriot President Nicos Anastasiades warned the deployment of troops to Libya marked "a dangerous threat to regional stability".

In a joint statement, the three leaders also said the bill, which allows for the deployment of non-combat troops to act as advisers and trainers for government forces against Gen Haftar, constituted a gross violation of a UN arms embargo on Libya.

Leaving aside the somewhat weird editing by the BBC which only tells us that the authorized mission was for advisers and trainer only in the 6th paragraph, I wonder what the parliamentary setup would be in other countries. To fix the discussion, does the US Congress for instance have to authorize deployment of trainers and advisors by the US Army in some foreign country, or would that be entirely an executive decision?

Answer 1

Whether or not it fit the spirit and intent of the War Powers Resolution of 1973, the US executive branch seems have managed sending combat forces, not trainers, just fine, to Lybia in 2011 without such approval.

Secretary of State Hillary Clinton testified to congress in March 2011 that the Obama administration did not need congressional authorization for its military intervention in Libya or for further decisions about it, despite congressional objections from members of both parties that the administration was violating the War Powers Resolution.

Note that the War Powers Resolution/War Powers Act, was passed in 1973, after the US left Vietnam, in order to avoid another POTUS again embroiling the country single-handedly into a foreign war, as first Kennedy, then Lyndon B. Johnson, had done. Starting with trainers and advisors provided by Kennedy in 1963.

In practice, this type of question seems a frequent subject of contention in the interpretation of legislative vs executive prerogatives for the US. I don't see trainers as being on the end of the scale that Congress would have a lot of success arguing about. Though maybe some budgetary ways to throttle a mission abroad could be found.