Během války lidé odešli.

Během means during in this sentence. It is a preposition, and it normally takes the genitive case.

So:

• válka = war
• během války = during the war

This is a very common pattern in Czech:

• během dne = during the day
• během roku = during the year
• během jednání = during the meeting / negotiations

So if you see během, you should expect the next noun to be in the genitive.

Because během requires the genitive, and válka is the nominative singular form.

The noun changes like this:

• válka = nominative singular
• války = genitive singular

So:

• válka = war
• během války = during the war

This is one of the main things Czech learners have to get used to: prepositions often force a particular case, so the noun form changes.

Both lidé and lidi can mean people, but they are used a bit differently.

In this sentence, lidé is the standard nominative plural form, which is what you need because lidé is the subject of the sentence.

• lidé odešli = people left

By contrast, lidi is very commonly used in everyday speech, but it is often:

• an accusative plural form
• or a more colloquial alternative in some contexts

For learners, the safest rule is:

• use lidé as the subject
• expect lidi very often in spoken Czech, especially as an object

Examples:

• Lidé přišli. = People arrived.
• Vidím lidi. = I see people.

Native speakers do use lidi a lot, but lidé is the more clearly standard form for the subject here.

The dictionary form is odejít, which means to leave, to go away, or to depart.

So the forms are:

• odejít = infinitive
• odešel = he left
• odešla = she left
• odešlo = it left
• odešli = they left

This verb is related to jít (to go) with the prefix od-, which adds the idea of away / off / from a place.

So odejít is literally something like to go away.

Because it is the past tense plural masculine animate form.

In Czech past tense, the verb agrees with the subject in number and, in the plural, often also in gender category.

Here the subject is lidé (people), which is treated as masculine animate plural, so the verb is:

• odešli

Compare:

• muži odešli = the men left
• ženy odešly = the women left
• děti odešly = the children left
• lidé odešli = the people left

So -li is the plural ending used with masculine animate subjects.

Because Czech grammar and real-world meaning are not always the same thing.

The noun lidé is grammatically treated as masculine animate plural, even though it refers to people in general, not just men.

That means verbs and adjectives agree with it as masculine animate:

• dobří lidé = good people
• lidé odešli = people left

This is a normal feature of Czech grammar. A noun’s grammatical gender controls agreement, even when the actual group is mixed.

This is mainly a question of aspect.

• odešli is from odejít, which is perfective
• odcházeli is from odcházet, which is imperfective

Very roughly:

• odešli = they left / they went away
  
  • focuses on the action as completed
• odcházeli = they were leaving / they used to leave / they kept leaving
  
  • focuses on the process, repetition, or ongoing nature

So:

• Během války lidé odešli. suggests a completed departure.
• Během války lidé odcházeli. would suggest that people were leaving over a period of time, perhaps repeatedly or gradually.

English often uses simple past for both ideas, so this difference can feel new to English speakers.

Yes. Czech word order is relatively flexible, because the endings show grammatical roles.

So these are all possible:

• Během války lidé odešli.
• Lidé během války odešli.
• Lidé odešli během války.

They all mean roughly the same thing, but the focus or emphasis changes slightly.

The original sentence, Během války lidé odešli, naturally sets the time frame first: During the war, people left.

That is a very common way to organize information in Czech: put known or contextual information first, then the main event later.

Because Czech does not have articles like English a and the.

So:

• válka can mean war, a war, or the war
• lidé can mean people or the people, depending on context

In během války, English naturally says during the war, but Czech simply uses the noun without any article.

Context tells you whether something is definite or indefinite.

Usually it means during the period of the war, not necessarily throughout the entire war from beginning to end.

So během války lidé odešli means that the leaving happened at some time within the war period, or generally in the course of the war.

It does not automatically mean that they were leaving continuously for the whole war. That kind of nuance would depend more on the verb choice, context, or extra wording.

Yes, often you can, but the tone is a little different.

• během války = during the war
• za války = in wartime / during the war

Za války is very common and often sounds a bit more idiomatic in everyday historical narration.
Během války is also completely correct and may sound slightly more neutral or formal.

So both are possible in many contexts:

• Během války lidé odešli.
• Za války lidé odešli.

The exact nuance depends on context, but both are normal Czech.

It can cover both ideas.

The verb odejít basically means to leave by going away. So depending on context, English might translate it as:

• left
• went away
• departed

Compared with English leave, Czech odejít often makes the movement away a little more visible.

So:

• lidé odešli = people left / people went away

The best English translation depends on the wider context, but grammatically odešli is a very normal verb for leaving a place.

You would probably switch to the imperfective verb:

• Během války lidé odcházeli.

That sounds more like:

• people were leaving during the war
• people kept leaving during the war
• people left gradually during the war

If you want to make the idea of gradual or mass departure even clearer, Czech often adds extra words, for example:

• Během války mnoho lidí odcházelo. = During the war, many people were leaving.
• Během války lidé postupně odcházeli. = During the war, people gradually left / were gradually leaving.

So the original odešli gives a completed fact, while odcházeli gives more of an ongoing process.