Learn Hardcore German: Ohne gutes Holz lässt sich kein Lagerfeuer anzünden, was wir an dem nassen Abend schnell gemerkt haben. - Without good wood you cannot light a campfire, which we quickly noticed on that wet evening.

The structure sich lassen + Infinitiv is a very common way in German to say that something can be done or is possible / not possible to do with that thing.

lässt sich anzünden literally: “lets itself be lit”
idiomatically: “can be lit”

So:

Kein Lagerfeuer lässt sich anzünden.
≈ No campfire can be lit.

You could also say:

Man kann kein Lagerfeuer anzünden.
Kein Lagerfeuer kann angezündet werden.

All three are grammatically correct. sich lassen often sounds a bit more neutral or matter‑of‑fact than using man, and slightly more natural than the full passive in everyday speech. It focuses on the do‑ability of the action.

Why is Holz in the form gutes Holz and not gutem Holz or gute Holz after ohne?

The preposition ohne always takes the accusative case.

ohne
- accusative

Holz is a neuter noun (das Holz), so in the accusative singular:

article: das → (often dropped in a general statement)
adjective ending: -es
noun: Holz

So you get:

ohne gutes Holz = without good wood

If it were masculine or feminine, the endings would change, for example:

ohne guten Wein (masc.)
ohne gute Kohle (fem.)

But with neuter Holz, accusative is gutes Holz.

Why is the sentence order Ohne gutes Holz lässt sich kein Lagerfeuer anzünden and not Ohne gutes Holz kein Lagerfeuer lässt sich anzünden?

German main clauses must keep the finite verb in second position (the V2 rule).

Here, the parts are:

Ohne gutes Holz – prepositional phrase, placed first for emphasis (topic)
lässt – the finite verb (must be in 2nd position)
sich kein Lagerfeuer anzünden – the rest of the clause

You could also say:

Kein Lagerfeuer lässt sich ohne gutes Holz anzünden.
Man kann ohne gutes Holz kein Lagerfeuer anzünden.

But in all main‑clause versions, the finite verb (here lässt) must be in the 2nd slot, counting whole phrases as one position. So Ohne gutes Holz kein Lagerfeuer lässt sich anzünden breaks the V2 rule and is wrong.

What is the function of sich in lässt sich kein Lagerfeuer anzünden? Is it really reflexive?

Formally, sich is a reflexive pronoun, but here it’s part of the fixed construction:

sich lassen + Infinitiv = can be done, is (not) possible

There’s no real “self‑action” like “the campfire lights itself”. Instead:

Kein Lagerfeuer lässt sich anzünden.
literally: No campfire lets itself be lit.
meaning: No campfire can be lit.

So you shouldn’t interpret sich with its usual reflexive meaning here. Treat lässt sich … anzünden as one unit expressing possibility / feasibility.

Why is it kein Lagerfeuer instead of kein Feuer or kein Lagerfeuer with an article?

Lagerfeuer is a neuter noun (das Lagerfeuer). In the sentence, kein replaces the indefinite article (ein):

ein Lagerfeuer → kein Lagerfeuer

Choose kein Lagerfeuer because the context is specifically about campfires, not just any kind of fire. A few contrasts:

kein Feuer – no fire at all (very general)
kein Lagerfeuer – no campfire (more specific)
kein offenes Feuer – no open fire

No extra article is needed; kein already functions as a determiner.

Why is there a comma before was and what does was refer to?

The part after the comma is a relative clause:

…, was wir an dem nassen Abend schnell gemerkt haben.

Here, was does not refer to a single noun. It refers to the entire preceding statement:

Ohne gutes Holz lässt sich kein Lagerfeuer anzünden,
was wir an dem nassen Abend schnell gemerkt haben.
→ … which (fact) we quickly realized that rainy evening.

In English you might use which referring to the whole idea:

Without good wood you can’t light a campfire, which we quickly realized that wet evening.

So:

The comma introduces a non‑restrictive relative clause.
was is a relative pronoun referring to the whole previous clause, not to a specific noun like Lagerfeuer or Holz.

Why is it was and not das or was das in the relative clause?

German uses was as a relative pronoun in two common cases:

After alles, nichts, etwas, viel, wenig:
- Alles, was ich habe…
Referring to an entire preceding statement or idea:
- Er ist zu spät gekommen, was mich nicht überrascht.

Here we’re in case 2: was refers to the whole idea that you can’t light a campfire without good wood. Using das alone as a relative pronoun here would be wrong (…*, das wir an dem nassen Abend…* is not idiomatic).

So was is the correct choice to refer back to the whole previous sentence.

Why is it an dem nassen Abend and not something like in dem nassen Abend or bei dem nassen Abend?

For time expressions, German often uses an + dative for a specific day or date:

an dem Abend → on that evening
am Montag → on Monday
am 24. Dezember → on the 24th of December

So:

an dem nassen Abend = on that wet evening
spoken and written more commonly as am nassen Abend (contraction of an dem).

Using in dem Abend for time is not idiomatic. bei would suggest during / at the occasion of, e.g.:

bei dem Konzert – at the concert

But for a specific evening as a time point, an (am) is the standard choice.

Why is nassen Abend in the dative, and why the ending -en on nass?

Because of an dem Abend:

an (in the time meaning on [a day/evening]) governs the dative case.
Abend is masculine: der Abend → dative singular: dem Abend.
With a definite article (dem), the weak adjective ending is -en:
- dem nassen Abend

So:

Preposition: an → dative
Article: dem (masc. dative singular)
Adjective ending in this pattern: nass → nassen

Hence: an dem nassen Abend.

Why is the word order in the relative clause … was wir an dem nassen Abend schnell gemerkt haben and not … was wir schnell an dem nassen Abend gemerkt haben or with haben earlier?

In German subordinate clauses, the finite verb goes to the end of the clause.

The clause is:

was – relative pronoun (first position)
wir – subject
an dem nassen Abend – time phrase
schnell – adverb
gemerkt haben – verb complex (Partizip II + finite verb haben)

In a subordinate clause, the entire verb complex must be at the end:

correct: … was wir an dem nassen Abend schnell gemerkt haben.
incorrect: … was wir an dem nassen Abend schnell haben gemerkt.

You can move schnell a bit:

… was wir schnell an dem nassen Abend gemerkt haben. (also correct, just a different emphasis)
… was wir an dem nassen Abend schnell gemerkt haben. (neutral, natural)

But haben must stay last, after the participle gemerkt, because that’s how perfect tense is formed in subordinate clauses: gemerkt haben at the end.

Why is gemerkt haben in the perfect tense here and not merkten in the simple past?

In spoken and informal written German, the Perfekt (haben/sein + Partizip II) is much more common for past events than the Präteritum (simple past) for most verbs.

wir haben gemerkt (Perfekt) – default in everyday speech
wir merkten (Präteritum) – possible, but sounds more written/literary or old‑fashioned for this verb

In subordinate clause word order:

Main clause: Wir haben das schnell gemerkt.
Subordinate: …, was wir schnell gemerkt haben.

So gemerkt haben is simply the usual spoken/written perfect tense form. Using merkten would sound stylistically marked or literary here.

Could you rephrase the German sentence in a simpler way that keeps the meaning?

Yes, for example:

Ohne gutes Holz kann man kein Lagerfeuer anzünden. Das haben wir an dem nassen Abend schnell gemerkt.

Or slightly more natural with contraction:

Ohne gutes Holz kann man kein Lagerfeuer anzünden. Das haben wir an dem nassen Abend schnell gemerkt.

These versions:

avoid lässt sich and the relative clause with was,
split the idea into two clearer sentences:
1. Statement of fact
2. When and how we realized it.

But the original is perfectly natural, slightly more compact and stylistically a little higher.