As mtwde said, German culture does not know ritual suicide as in Japan. Concerning Erwin Rommel I recommend you to read the section "Death" in https://en.wikipedia.org/wiki/Erwin_Rommel. His suicide was related to the "20 July plot" in 1944 which was an attempt by German officers to assassinate Adolf Hitler (and which unfortunately failed). See https://en.wikipedia.org/wiki/20_July_plot. Although it is not clear whether Rommel was involved, he was suspected to be a "traitor". The consequence would have been to be brought to the Volksgerichtshof (People's Court), an institution which was an instrument of injustice and Nazi ideology and will be a dishonour for Germany forever. Hitler himself offered Rommel to commit suicide instead of being brought to the Volksgerichtshof. Rommel accepted to protect his family. But the point is that Rommel was something like a national hero and bringing him to the Volksgerichtshof would have been disavowing for the Nazi regime. His suicide was hushed and it was claimed he had died of either a heart attack or a cerebral embolism. He was given a state funeral and Hitler ordered an official day of mourning in commemoration.
Concerning suicide: Modern European history started some centuries after the final fall of the western part of the Roman empire in 476. In the middle ages more or less all European countries were Christian kingdoms. The personal identity of a knight was that of a Christian knight (although not all of them always acted in a Christian way). The church condemned suicide as a severe sin. In fact, the fifth of the Ten Commandments of the bible says "Thou shalt not kill" (here "kill" means "murder", not for example to kill in war), and suicide was viewed as murdering oneself. This is reflected in the German word "Selbstmord" for suicide - its meaning is precisely to murder oneself. Thus suicide was no option for a Christian knight (though it certainly happened). The time of knights is long gone, but also in modern German armies suicide was not really common (with the remarkable exception of the German defeat in 1945). In fact, the trial to commit suicide (if the soldier surived) was prosecuted as "subversion of national defense".
You may be interested in the codex of honour in the early middle ages. A famous example is the Hildebrandslied (see https://en.wikipedia.org/wiki/Hildebrandslied) which reflects old traditions before the Christianization of the Germanic tribes.