Why "hätte" instead of "würde ... haben"?

Question

I found these two phrases next to each other in a text, and it made me wonder why they are formulated differently, while in english and any other language I know they are expressed using the same tenses.

Wenn ich du wäre, würde ich das nicht tun.

(if I were you, I wouldn't do that).

This is as I expected. But this:

Wenn ich das gewusst hätte, dann hätte ich dagegen protestiert.

(Had I known that, I would have protested against it).

I expected this second one to be

Wenn ich das gewusst hätte, dann würde ich dagegen protestiert haben.

Is my understanding correct?

Answer 1

German has 2 ways to build the conditional. You can either use the verbs conjunctive forms or you can use the auxiliary werden.

Here's an example for "present conditional"

Ich würde einen Kaffee trinken.

Ich tränke einen Kaffee.

Both ways do express the same idea and which is used depends mainly on the verb itself. Haben, sein, the modal verbs as well as some common regular verbs tend to be used with their own form while others are always build using werden.

German verbs do not have their own form to express "past conditional". So to include the idea of past you always need an auxiliary (either haben or sein). This then gets to carry the information about conditional. And since haben and sein mostly use their own form you end up with

Ich hätte einen Kaffee getrunken.

instead of

Ich würde einen Kaffee getrunken haben.

There are some subtle differences between those two sentences. They have to do with the difference between the preterit and the perfect tense but for the most part they mean the same and the first version is just way more colloquial.

Answer 2

Disclaimer: I am by far not a native speaker, not even an advanced learner, but here goes my take.

Konjunktiv II can be formed in two ways: with umlauting(if possible) the vowel of the Präteritum and adding -e at the end, or by using würde + Infinitiv. Incidentally, würde itself is the Konjunktiv II form of werden.

For example:

Infinitiv: gehen

Konjunktiv II: ginge, würde gehen

Infinitiv: kommen

Konjunktiv II: käme, würde kommen

There are some verbs that have an irregular (weak) Konjunktiv II form, such as

Infinitiv: helfen

Konjunktiv II: hälfe/hülfe, würde helfen

Infinitiv: sterben

Konjunktiv II: stürbe, würde sterben

Now, in colloquial speech, the direct form of Konjunktiv II (without würde), especially for those verbs that have a special irregular Konjunktiv, is seldom used, the exception being auxiliary verbs like sein, haben, werden, etc. The direct form sounds quite literary or dated.

Example:

Ohne dich stürbe ich.

This sounds quite poetic and literary, one wouldn't say it in everyday speech. Instead, one would say

Ohne dich würde ich sterben.

But one wouldn't normally say

Wenn ich das gewusst hätte, dann würde ich dagegen protestiert haben.

Because haben is an auxiliary verb, and for those the direct form of Konjunktiv is used

Wenn ich das gewusst hätte, dann hätte ich dagegen protestiert.