Strategy Page recounts some of the recent the bureaucratic snags between NATO countries in eastern Europe when troops need to cross inter-alliance borders:
In early 2015 Operation Dragoon Ride rolled through Central Europe to send a message to Russians. From March 20th to April 1st, an US Army squadron returning from Atlantic Resolve NATO exercises took an unusual route back to its base in Germany, after spending three months in training facilities in Poland, Lithuania and Estonia. The unit involved was the 3rd Squadron (battalion) of the 2nd American Cavalry Regiment. This unit refers to itself as dragoons (an ancient term for horse mounted infantry) and the movement operation was called Dragoon Ride and the apparent reason for it was to demonstrate to the locals as well as the Russians that American armored units could reach the East European NATO nations by road, as well as by ship, aircraft or rail. Dragoon Ride purposely rode close to the Russian border, often in full view of Russians and Russian media. The American troops frequently stopped in towns and villages so the locals could meet their allies, take pictures and quietly enjoy the pain this demonstration was causing the increasingly aggressive Russians.
But what was not publicized, and what the Russian government knew full well, was that this road movement took the efforts of hundreds of unseen troops and bureaucrats to deal with the paperwork. For all of 2015 it required nearly 6,000 travel documents to be prepared, filed and approved to get foreign military vehicles across East European borders. Some of these documents take several weeks to get approved and operations like Dragoon Ride required hundreds of them and nearly as many NATO local government personnel were involved with this paperwork as were actually participating (500 troops) in the actual Dragoon Ride (of 120 vehicles). While all these rules and approvals would not stop invading Russians they would, in theory, slow down reinforces from the West.
The pile of paperwork and weeks required to handle it were used as very concrete evidence to persuade the East European nations to streamline the process, a lot, or have themselves to blame if reinforcements did not arrive in a timely fashion. As usual a compromise was worked out. Thus eight NFIUs (NATO Force Integration Units) were organized, each consisting of 40 troops trained and equipped to handle the paperwork and traffic control measures required to get military convoys across eastern borders as quickly as possible. The NFIU work out of embassies and stay in constant touch with the border control bureaucracies of the East European nations involved. NFIUs also arrange for rest areas and resupply for the convoys.