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Prepositions after verbs

Defend by or defend against?

Use defend against for protection from danger, attack, or criticism. Defend by is not a standard fixed pattern, though by can introduce a method or agent.

Quick answer

Which preposition follows defend?

Use defend against to describe protection from something harmful: defend against attacks. Defend by usually introduces a method, as in defend itself by raising prices.

The walls defend the city against invasion.
She defended herself against false accusations.
The company defended its decision by citing new data.

Choose the pattern by meaning

These forms are not interchangeable. Choose the construction by meaning, not by which preposition appears most often.

1
defend against + threat

Protection from harm or attack

Use against for enemies, criticism, disease, or danger.

Vaccines help defend the body against infection.
2
defend + object

Supporting or protecting directly

Defend can also take a direct object without a preposition.

Lawyers defended the client in court.
3
defend by + method

Explaining how something is defended

By can introduce the method used for defence, not the threat.

The animal defends itself by releasing a strong smell.

See the difference in context

The same subject can take different constructions because each sentence answers a different question.

Construction
Example
Meaning
defend against + threat
The software defends against viruses.
Standard pattern for protection from danger.
defend by + method
They defended the policy by presenting evidence.
By introduces the means or method.
defended by + agent
The village was defended by local volunteers.
Passive structure naming the defender.

Common mistakes

Some combinations appear in real text but do not mean what learners often assume.

Using by instead of against for threats

Use against when naming the danger or attack.

✕ The walls defend the town by enemies. ✓ The walls defend the town against enemies.

Confusing method with threat

By introduces how the defence happens, not what it protects from.

✕ She defended herself by criticism. ✓ She defended herself against criticism.

Quick practice

Choose the expression that matches the intended meaning.

1. The army defended the border ___ attack.
2. The company defended its actions ___ publishing documents.
3. The castle was defended ___ skilled archers.

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Frequently asked questions

Is defend against the main pattern?

Yes. It is the standard way to express protection from danger or attack.

Can defend be followed directly by an object?

Yes. For example: defend the country or defend your position.

Why does by sometimes appear after defend?

By may introduce a method or an agent in passive voice, not the threat itself.

dabble, in, dabble, with "damage to" or "damage by"? dance to, with, on, in or for? "dangle from" or "dangle in"? dare to, for, on, as or at? dash to, into, out, from or on? daydream about, for, in, of or on? "debate in", "debate on" or "debate with"? deceive by, in, into, on or about? "decide on", "decide to" or "decide by"? declare in, by, on, to or as? decline in, by, from, to or for?

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