Past-before-past. The tense you only really need with nachdem.

The Plusquamperfekt is formed exactly like the Perfekt, but with the auxiliary verb in Präteritum instead of Präsens. Choose hatte (most verbs) or war (motion and state-change verbs — the same rule as Perfekt haben/sein), conjugate the auxiliary for the subject, then add the Partizip II of the main verb at the end. Examples: Er hatte das Buch gelesen (he had read the book); Sie war nach Hause gegangen (she had gone home).

The Plusquamperfekt expresses an action that was completed before another past action — past-before-past. The canonical context is nachdem-clauses: "After I had done X, Y happened." Outside of nachdem, it also appears in written and literary narrative as a past-before-past device, but this usage is uncommon in everyday spoken German. Germans do not use Plusquamperfekt the way English uses past perfect as a politeness strategy; its function is purely temporal sequence.

Both tenses use haben or sein plus Partizip II, and they share the same Partizip II forms and the same haben/sein decision rule. The difference is perspective: Perfekt expresses "past viewed from the present" (Ich habe gegessen — I have eaten, relevant now); Plusquamperfekt expresses "past viewed from another past moment" (Ich hatte gegessen, bevor er ankam — I had already eaten before he arrived). In practice, Plusquamperfekt only appears when there are two past events and you need to signal which one came first.

The same rule applies as in Perfekt: sein-verbs (motion verbs, change-of-state verbs, and sein/bleiben/werden) use war (Präteritum of sein); all other verbs use hatte (Präteritum of haben). If you know which auxiliary a verb takes in Perfekt, you automatically know which it takes in Plusquamperfekt — hatte is the Präteritum of haben, and war is the Präteritum of sein.

When using nachdem (after), the subordinate clause must use Plusquamperfekt and the main clause uses Präteritum or Perfekt. Example: Nachdem er das Buch gelesen hatte, ging er ins Bett (subordinate clause = Plusquamperfekt gelesen hatte; main clause = Präteritum ging). Using Perfekt in the nachdem-clause — Nachdem er das Buch gelesen hat, ging er ins Bett — is grammatically incorrect in standard written German and is the most common sequence-of-tenses error on B1 exams.

Yes. In free narrative, two sentences can establish a past-before-past sequence without a conjunction: Er war müde. Er hatte den ganzen Tag gearbeitet. (He was tired. He had worked all day.) This usage is mostly literary or journalistic — in everyday spoken German, people typically use Perfekt plus a time adverb such as danach or vorher instead of Plusquamperfekt for free narrative.

Nachdem (after) requires Plusquamperfekt in its subordinate clause: Nachdem er gegessen hatte, schlief er (the eating came first, so it goes into Plusquamperfekt). Bevor (before) does not require Plusquamperfekt — the subordinate clause typically uses the same tense as the main clause, usually Präteritum or Perfekt: Bevor er schlief, aß er. The rule of thumb: nachdem flips the earlier action into Plusquamperfekt; bevor keeps both clauses in the same tense.

The nachdem-clause sequence-of-tenses rule is one of the most consistently tested B1 grammar points: exam writers specifically target the error of using Perfekt instead of Plusquamperfekt in nachdem-clauses. B1 reading texts — newspaper reports, short stories, formal emails — frequently use Plusquamperfekt in narrative passages, so passive recognition of the form is essential for comprehension. Learners who can form and recognise Plusquamperfekt reliably gain points on both the writing and reading components.