While the armed forces available to NATO far outnumber those of Russia, there is a major impediment to assembling and moving those forces to the aid of NATO nations bordering Russia. That enemy is the ancient bureaucracy that controls the movement of foreign troops crossing borders, even those forces coming to your aid. This was demonstrated in early 2015 when an U.S. Army mechanized battalion made a very well publicized road march from Poland, Lithuania and Estonia back to its base in Germany. The American battalion required hundreds of hours of effort to complete the paperwork and get the permissions required to cross so many borders in military vehicles.
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.
Thus NFIUs ensure that the routes used have roads and bridges that can handle the heavy trucks and armored vehicles involved. This is a crucial matter in East Europe. Since the 1950s West European nations have constantly upgraded and maintained roads and bridges to handle heavy vehicles, but East Europe has not. The dozens of Russian divisions stationed in East Europe until 1990 were brought in piecemeal over decades, often transporting heavy equipment by ship or rail. Moreover NATO heavy equipment is heavier than their Russian counterparts so even East European bridges built to handle Russian tanks often cannot deal with heavier M-1s and Leopards.
The NFIUs must maintain the new database on 15,000 kilometers of East European roads and hundreds of bridges. Available cross country routes have also been mapped and put into the database. Because of such road and bridge restrictions the Dragoon Ride forces used 20 ton Stryker wheeled armored vehicles and not the heavier 63 ton M-1 tanks and 27 ton M-2 infantry fighting vehicles that usually accompany Strykers.