• Reich #0: The ancestral Germanic speakers. Since the Germanic languages share several several distinctive features (for more, see this appendix on linguistic detective work), it is clear that there had once been some community that had spoken the ancestor of the Germanic languages. From historical evidence, their residence had been what is now northern Germany and southern Denmark about 2000-2500 years go. The Jastorf artifact style is found from several archeological sites at the appropriate places and times, so those sites were likely the physical remains of the ancestral Germanic speakers.
• Reich #0.5: Not really a nation, but a lot of early Germanic tribes, such as those that had defeated the Roman Legions at Teutoberg Forest.
• Reich #1: The Holy Roman Empire, founded by Emperor Charlemagne of France in 800 CE; it lasted a thousand years before being broken up in the early 19th cy. It had been neither holy, nor Roman, nor an empire; but a loose confederation of states and duchies and principalities and the like in Germany and Italy and nearby. An alternative is the Prussian State, which had become prominent in the 18th century (it was in what is now Eastern Germany, northern Poland, and the Kaliningrad area; the latter town had once been Koenigsberg).
• Reich #1.5: The early-19th-cy. Zollverein or Customs Union; several western-German states dropped border tariffs between them, allowing them to act as the economic equivalent of a single nation. However, it did not include Prussia or Austria.
• Reich #2: Prussian Chancellor Bismarck's unification of Germany in 1871; a unification that omitted Austria. It lasted until Kaiser Wilhelm's abdication at the end of World War 1. Austria itself was a multi-ethnic empire that started to split apart, becoming Austria-Hungary in that time.
• Reich #2.5: The Weimar Republic, from the end of World War 1 to 1933. It was never very stable, and it was opposed by a strong right wing that had hankered for a Bismarckian Good Old Days. Austria was broken up, with the name sticking to the "German" part of the old empire.
• Reich #3: The regime of the National Socialist German Workers' Party, better known as the Nazi Party (the aforementioned villains). It had lasted from 1933 to 1945, a little over 1% of its hoped-for lifetime of 1000 years. It was dismembered by its enemies at the end of World War 2 in 1945. Austria was annexed by it in 1938, and detached in 1945 after its defeat.
• Reich #3.5: West Germany, from the end of World War 2 to 1989. It was formed from the largest postwar partition of Germany; East Germany may not be worth counting, and Austria was clearly not a part of it.
• Reich #4: It is not clear whether a reunified Germany truly counts as a new Reich or whether it is simply the annexation of East Germany by West Germany without fundamental change in the latter. Austria is still independent, however.

It's been suggested to me by Scott Erb that "reich" may be inappropriate for some of these entries; he suggests something like:

Interwar Germany	Weimar Republic	First Republic
West Germany	Bonn Republic	Second Republic
Reunified Germany	Berlin Republic	Third Republic

Appendix: Linguistic detective work

Though determining relationships between languages has no shortage of pitfalls, such as borrowed words and parallel developments, there are some features of languages that tend to be inherited from their ancestors, such as basic vocabulary and grammatical features. These can be used to classify languages and to work out their family trees. For example, several northern-European languages, including English, Dutch, German, Swedish, and Icelandic, are classified as Germanic languages, and these, along with several more European and western-Asian languages, are classified as Indo-European languages.

The Germanic family has several distinctive grammatical features; these I will illustrate with parallel English and German examples.

Germanic verbs come in two classes: strong and weak. Strong verbs have past tenses and some derived nouns with vowel shifts:

to sing	singen
I sing	ich singe
I sang	ich sang
I have sung	ich habe gesungen

Weak verbs have past tenses with the suffix -ed and its cognates, like German -te. The vowel shifts, sometimes called "ablaut", are a fossilized relic of a feature of the ancestral Indo-European language; it survives in various degrees in other Indo-European languages. The -ed suffix, however, has an unclear origin, despite an abundance of speculation. We can be sure that these features are ancestral and not borrowed, because word-morphology features, especially irregular ones, are seldom borrowed, even when large amounts of vocabulary get borrowed. So we can be sure that the ancestral Germanic speakers had had both strong verbs and weak verbs.

Most Germanic languages have "strong" and "weak" adjective declensions, depending on what had preceded that adjective. Though modern English lacks such a distinction (adjective declension has disappeared except for this/these and that/those), Old English had such a distinction. Examples:

a third realm	ein dritter Reich	(dritter is strong)
the third realm	der dritte Reich	(dritte is weak)

Germanic languages often have verb-preposition "phrasal verbs", like:

to come out	herauskommen
I come out	ich komme heraus
I came out	ich kam heraus
I have come out	ich bin herausgekommen

While in English, the preposition always follows the verb, in German, it alternates between prefixing and following the verb.

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