Germany's constitution takes a quite firm stand on the purpose of the Bundeswehr (even though that's increasingly been ignored since the early 90's):
Article 87a [Armed Forces]
(1) The Federation shall establish Armed Forces for purposes of defence. Their numerical strength and general organisational structure must be shown in the budget.
(2) Apart from defence, the Armed Forces may be employed only to the extent expressly permitted by this Basic Law.
German national defence is nowadays alliance defence; either NATO or EU defence. Either way, the most significant and least unlikely scenario for the Bundeswehr would be a conflict in the East.
Troops stationed in Germany could be first or at the latest second week responders to a border conflict or similar on an Eastern ally's border. Only airborne troops could deploy more quickly, and again airborne troops stationed in Germany could likely be amongst the very first.
Now if we took collective defence seriously and did not spend much attention on great power gaming (small wars) instead, what would the Bundeswehr need to do?
I suppose it would need to take a look at how to deploy a meaningful brigade-sized airborne force in few days to the East of Warsaw and at how to deploy several combat brigades, higher echelon support units and lots of supplies to the East of Warsaw on road within at most a week. It is possible to drive the distance in two days at most (tracked vehicles probably three days, with a substantial share being broken down en route). Organising tank travel by rail could add many days to the duration of the movement, and rail lines could be interrupted anyway.
Road movement into the Baltic region would be very troublesome, as the road connection between Poland and the Baltic has almost no alternatives. There's but one fine road and a lesser one - both aren't even close to motorway standards. Maybe the EU should think about improving the infrastructure there.
We had some exercises with entire brigades moving hundred of kilometres in a day on roads alone during the Cold War, but such exercises are expensive in spare parts and fuel. We rarely do such movements these days. A bi-annual deployment exercise to East of Warsaw for every German brigade would probably be a major diplomatic irritant anyway.
The Luftwaffe would also need to look closely at at least how to deploy wings to East German airbases and commercial airports, if not motorways. Such movements would need to happen amidst air-refuelling-enabled combat missions (or patrols) and only few military cargo aircraft would be available if there's a parallel airlift of airborne troops. So again, lots of trucks would need to move over the road network to their destinations.
The navy finally would need to think about what the winter-time ice on the far eastern Baltic Sea means for naval operations. Our submarines could hardly interfere with amphibious hovercraft movements or even truck movements over the ice, after all.
A much less likely scenario would require German military power in the Mediterranean (not require it militarily, but rather politically). Naval forces (frigates, subs, mine countermeasures, supply ships) could cruise at very different cruise speeds to the Med through the Strait of Gibraltar (with frigates arriving first).
The Luftwaffe and airborne troops could arrive within a week, but only with very much stretched supply lines. A deployment of the heavier army brigades to the Mediterranean region would likely lead to administrative movement by rail, and could take weeks till the troops and their supplies are ready for action. Again, peacetime exercises could help to reduce this time and to improve the shape of the arriving forces.
This is the kind of deployability we should think about. By comparison, a deployment of less than brigade-sized forces with little heavy material into a distant civil war is not exactly a topic close to the national interests or the constitutional mission.
This blog post has probably provoked the ubiquitous responses; maybe you considered this all Cold War-era talk, as there are no real threats to NATO's frontiers.
Well, in this case feel free to try to reconcile this thought with the inability of the marginal benefits from small wars missions to justify the gazillions of military spending in Europe. Either it makes sense to prepare for actual defence OR small wars are profitable and able to justify more than € 20bn military budget of Germany annually. I suppose the ISAF mission cannot be valued at anywhere close to €20bn annually, so I suppose the real job is the constitutional job: (collective) defence.
Let's focus at this instead of being easily distracted by pointless small wars.