Learn Hardcore Russian: Мы должны были уехать в июле, но из‑за работы остались в городе. - We had to leave in July, but because of work we stayed in the city.

мы должны были уехать ≈ “we were supposed to leave / we had to leave.”
The auxiliary были puts the obligation into the past: they previously had that obligation or plan.

So the structure is:

мы должны были
- infinitive (уехать)
  “we were supposed (in the past) to leave.”

It implies a planned or expected action in the past, which in this sentence did not happen because of the second part: …но из-за работы остались в городе.

Why is it должны были уехать and not something like надо было уехать? What’s the difference?

Both are possible, but they have slightly different nuances:

должны были уехать
– “were supposed to / were obligated to leave.”
– Sounds a bit more like a duty or strong expectation, sometimes tied to a plan, schedule, arrangement.
надо было уехать
– “should have left / it was necessary to leave.”
– More about practical necessity or hindsight (“we really should have left”).

In this sentence, должны были fits well because it suggests there was a concrete plan or arrangement to leave in July (maybe tickets, reservations, agreed dates, etc.), which got canceled because of work.

Why is уехать (perfective) used and not уезжать or ехать?

Russian uses aspect (perfective vs. imperfective) even with modal meanings like “must / should”.

уехать (perfective) = to leave, depart (as one complete action, with the result that you are gone).
уезжать (imperfective) = to be leaving / to leave repeatedly or in progress.
ехать is more like “to go (by transport)” in progress; with “leave” meaning it’s less precise here.

With должны были, a perfective infinitive often expresses a single, whole, intended event:

мы должны были уехать ≈ “we were supposed to (at some point) leave and be gone.”

Even though they did not actually leave, Russian still uses the perfective here because it describes the nature of the planned action: one completed departure, not an ongoing process.

If they didn’t actually leave, is it normal in Russian to use perfective уехать for something that didn’t happen?

Yes. This is very typical and can feel strange for English speakers.

Russian often uses perfective with verbs of planned actions, even if those actions do not occur:

Я хотел позвонить тебе, но забыл.
“I wanted to call you, but I forgot.” (позвонить is perfective, but the call never happened.)

Similarly:

Мы должны были уехать в июле, но…
“We were supposed to leave in July, but…” (they didn’t leave).

Perfective here describes the intended result (a single completed departure), independent of whether it actually took place. Context (or explicit negation) tells you that the plan was not carried out.

What is the difference between уехать “to leave” and a neutral “go somewhere”? Does уехать imply transport?

Уехать strongly implies leaving by some means of transport (car, train, bus, etc.), and crucially, it implies departure from a place.

уехать из города – to leave the city (by transport).
уйти из города – to leave the city (on foot or more abstractly).

In your sentence, уехать is natural because leaving the city usually involves travel by transport. It focuses on departure and resulting absence, not just moving within the city.

Why is it в июле and not something like в июнь? What case is that?

В июле is the prepositional case of июль (July):

nominative: июль
prepositional: в июле

When you talk about something happening in a month (in July, in August, etc.), Russian uses в + prepositional:

в июле – in July
в августе – in August
в марте – in March

В июнь would be incorrect in this meaning. The prepositional is the standard case for “in [month]” when indicating time.

Why is из-за работы used, and what case is работы in?

Из-за is a compound preposition that always takes the genitive case:

из-за работы – “because of work / due to work.”

Here, работы is the genitive singular of работа.

Some key points about из-за:

It’s often used for reasons that are obstacles, problems, or inconveniences:
из-за пробок, из-за болезни, из-за дождя.
It can sound a bit more negative or external than из-за alternatives like из-за того, что… or потому что…, which introduce a whole clause.

So из-за работы остались в городе = “(we) stayed in the city because of work (and this was the obstacle to leaving).”

Could we use потому что instead of из-за работы? How would the sentence change?

Yes, you could say:

Мы должны были уехать в июле, но потому что была работа, остались в городе.
(usually improved to …но потому что у нас была работа, мы остались в городе.)

Differences:

из-за работы: short, compact, focuses on “work” as an external cause/obstacle.
потому что introduces a full clause with a verb:
потому что (у нас) была работа – “because we had work.”

Both express cause, but из-за работы is more concise and common in this exact kind of sentence.

Why is остались (perfective) used and not оставались (imperfective)?

остаться → остались (perfective past) = “ended up staying; remained (as a completed result).”
оставаться → оставались (imperfective past) = “were staying / used to stay / kept staying (emphasizes duration or repetition).”

In your sentence:

…но из-за работы остались в городе.

They want to say: “instead of leaving, the final result was: we stayed in the city.” That’s a single outcome, so perfective остались is natural.

If you said оставались, it would sound more like:

“we were (for some time) staying in the city because of work,”
focusing on the ongoing process of staying, not on the contrast between planned departure and final outcome.

Why is it в городе and not в город?

The difference is direction vs. location:

в город (accusative) – to the city, movement toward:
Мы поехали в город. – “We went to the city.”
в городе (prepositional) – in the city, location:
Мы остались в городе. – “We stayed in the city.”

Since they stayed in the city (did not move into it), Russian uses в городе (prepositional, location), not в город (direction).

Could the word order be …но остались в городе из-за работы? Is that OK?

Yes, that word order is also grammatically correct:

Мы должны были уехать в июле, но остались в городе из-за работы.

The meaning is the same. Russian word order is relatively flexible. Typical patterns:

из-за работы остались в городе – slightly emphasizes “because of work” as the cause.
остались в городе из-за работы – more neutral, “we stayed in the city because of work.”

Both are natural; the original version puts the reason earlier, right after но, which slightly highlights the contrast and cause.

Why do we need the comma before но?

In Russian, но is a coordinating conjunction similar to “but.” It connects two clauses:

Мы должны были уехать в июле – first clause.
(мы) из-за работы остались в городе – second clause (subject мы is omitted but understood).

When но joins two clauses, Russian punctuation rules require a comma before но:

…уехать в июле, но из-за работы остались в городе.

This is the same principle as in English: “We had to leave in July, but we stayed in the city because of work.”