Learn Hardcore Korean: beoseuga gojang naseo georeogage doeeosseoyo. - Because the bus broke down, I ended up walking.

걸어갔어요: a plain past fact — “I went on foot.”
걸어가게 되었어요: “I ended up going on foot” — it highlights that circumstances (the bus breaking down) led to the outcome, not a deliberate plan.
Nearby contrasts:
- 걸어가기로 했어요 = “I decided to go on foot.”
- 걸어가야 했어요 = “I had to go on foot.” (obligation/necessity)

Is -게 되다 basically the same as “had to”?

Not exactly. -게 되다 describes an outcome that came about due to circumstances, often outside your will. English often translates it as “ended up -ing,” though it can feel like “had to” in context. If you want to explicitly say obligation, use -아/어야 했다 (e.g., 걸어가야 했어요).

Why use -아서/어서 in 고장 나서? How is it different from -(으)니까 or 때문에?

-아서/어서 marks a natural cause-result chain: bus broke → result happened. It sounds neutral and matter-of-fact here.
-(으)니까 often presents a reason/explanation (sometimes more subjective or speaker-centered). You could say 버스가 고장 나니까 걸어가게 되었어요, which is also fine; nuance is minimal here.
때문에 is used with nouns (or -기 때문에 with verbs): 버스가 고장났기 때문에 걸어가게 되었어요 or 버스 고장 때문에…. Slightly heavier/more formal tone.

Where does 나서 come from? Why not 났어서?

나서 is 나다 + -아서/어서. With -아서/어서, you don’t put a past-tense marker in that first clause. So:

Correct: 버스가 고장 나서 늦었어요.
Unnatural: 버스가 고장 났어서 늦었어요. This pattern is general: 비가 와서는 맞고 비가 왔어서는 보통 쓰지 않아요.

Should it be 고장 나서, 고장이 나서, or 고장나서?

The textbook/careful form is 고장이 나서 (“a breakdown happened”), and you’ll see it a lot in dictionaries and formal writing.
In everyday writing/speech, 고장 나서 is also very common and natural.
You’ll also encounter the fused 고장나서; many people write it this way in informal contexts. For tests or very formal contexts, prefer 고장이 나서. In casual contexts, any of the three will be understood.

Why is it 버스가 and not 버스는?

버스가 marks the bus as the grammatical subject and tends to introduce or focus new information (“It’s the bus that broke down…”).
버스는 would topicalize it: “As for the bus, since it broke down…” Use 는 if the bus is already the topic of conversation or you’re contrasting it with something else.

Is 걸어가다 one word? Can I write 걸어 가다 or 걸어서 가다?

걸어가다 is commonly written as one word and is perfectly standard for “to go (somewhere) on foot.”
걸어서 가다 is also very common and emphasizes the means (“go by walking”). Both sound natural.
걸어 가다 with a space can appear when treating 가다 as an auxiliary, but for this meaning most people write 걸어가다 or say 걸어서 가다.

Could I say 걷게 되었어요 instead of 걸어가게 되었어요?

걷게 되었어요 = “I ended up walking” (activity of walking, no destination implied).
걸어가게 되었어요 = “I ended up going (to a place) on foot.” Because 가다 adds the sense of heading to/arriving at a destination, it matches this context better.

What’s the difference between 되었어요 and 됐어요?

They’re the same grammatically and semantically. 됐어요 is the standard contraction of 되었어요 and is more common in speech and everyday writing. Use 되었어요 if you want a slightly more formal or careful look.

The subject “I/we” isn’t written. Is that normal? How would I include it?

Yes, Korean often drops obvious subjects. If you want to include it:

저는/저희는 버스가 고장 나서 걸어가게 되었어요. The pronoun clarifies “I/we,” but it isn’t necessary if context already makes it clear.

Can I say 고장 나고 걸어갔어요 instead of 고장 나서?

-고 mainly sequences events (“and/and then”). 고장 나고 걸어갔어요 is understandable but sounds like a simple list. If you mean a cause-result relationship, -아서/어서 is the natural choice: 고장 나서.

What’s the difference between -게 되다 and -게 하다? Could I say 걸어가게 했어요?

-게 되다: an outcome happened to the subject due to circumstances (“ended up -ing”).
-게 하다: someone/something made someone do it (“made/let someone -”). So 걸어가게 했어요 means “(I/they) made (someone) go on foot,” which is a different meaning.

Is 버스가 고장 나서 걸어가야 했어요 also correct? How does it differ?

Yes, it’s correct. 걸어가야 했어요 emphasizes obligation/necessity (“I had to go on foot”). 걸어가게 되었어요 emphasizes the situational outcome (“I ended up going on foot”). Both fit here; choose based on the nuance you want.

How would I say this more formally?

버스가 고장 나서 걸어가게 됐습니다.
Slightly more formal/explicit: 버스가 고장이 나서 걸어서 가게 됐습니다.

Any pronunciation tips, especially for 됐어요?

됐어요 is pronounced roughly like [dwae-ss-eo-yo], with 되 → [dwe]/[dwae] and the ㅆ sound clearly articulated.
In 고장 나서, say it smoothly as [고장나서]; many speakers link 고장 and 나서 without a pause.
걸어가게 flows as [거러가게]; the ㄹ sound taps lightly.

What exactly is the -게 in 걸어가게 되었어요?

-게 is an adverbializer. With verbs, V-게 되다 means “to come to do V / end up doing V.” You can think of it as turning the action into the manner/result that “becomes” true:

가다 → 가게 되다 (it becomes so that one goes)
하다 → 하게 되다 (it becomes so that one does)