Correct me if I'm wrong, but before Germanic people became a centralized nation they were kind of nomadic and travelled in tribes. As a result, their warfare resembled that of guerrilla warfare where they would attack in smaller numbers for the purpose of gaining wealth. They lacked centralized leadership and attacked as loose bands of people instead of as a united force. I recently read that they made up a large number of the mercenary force during the 18th and 19th century.
I may be making a large leap here in asking this question, but was this at all linked to Germanic tribes' history of being raiders and having a lack of centralized leadership during their warfare? In short, can we link older Germanic culture to Germans being predispositioned to being mercenaries later in history?
In my opinion, that's a bit too far of a stretch.
The period of time when the Germanic tribes were primarily nomadic was well over two millennia ago in the classical era.
The Germanic culture had undergone thousands of years of change including massive societal changes influenced by the Romans and from the adoption of Christianity.
Calling the 18th and 19th century mercenaries 'Germans' is a bit of an anachronism. While the concept of Germany as a nation existed, the idea of nationalism had not fully developed and so these mercenaries for example, would mainly view themselves as Hessians, or Prussians rather than Germans.
In response to your actual question, sort of. Germany existed as a lose confederation of city states and duchies that were more or less independent for most of the 18th century. Compared to their neighbouring empires, these states lived in relative peace - The British, French and Spanish empires were constantly embroiled in massive wars. Mercenaries were often sought after to provide expertise and manpower to help them in these conflicts. It just happened to be that most of the neutral parties in the war who were willing to be contracted as mercenaries were German. These small German states had professional armies which their princes often hired out.
However, this cannot be directly traced back to their tribal origins as that was far too long ago to have any significant impact on the propensity of German mercenaries thousands of years later.
Did you forget the Holy Roman Empire? For nine hundred years, Europe's premier political power controlled nearly all the land we now call Germany. After that, it was divided into numerous feudal bits which we reconsolidated into the German Confederation in 1814.
The landesknecht, a mostly-German group of badass mercenaries, were raised by the HRE to put the Swiss out of business. The Swiss. You know those bankers and guys who make chocolate? They were the gold standard for heavy infantry. Lots of predisposition there.
Later on there were the Hessians. At that point, Germany was still a conglomeration of mostly-independent states. Most, perhaps all, of them had independent armies that they hired out. The British hired lots of them during the American Revolution, for example. The Empire begins in 1871.
Go back far enough and every population is nomads. There's something to be said for Mongols and Parthians, people living in a certain culture which happens to very applicable to militariam. But you can't extrapolate from centuries upon centuries back without the stuff inbetween. India and Zimbabwe had massive empires once.