The short answer is: it was almost certainly a slow decline over centuries, not a single catastrophic fire. Julius Caesar may have played a role in damaging part of the library's collections, but the idea that he single-handedly destroyed the entire Library of Alexandria is not supported by the evidence.
Here's what historians think happened.
The Library was more than just one building
The Library of Alexandria was founded in the 3rd century BCE under the Ptolemy I Soter and expanded by his successor Ptolemy II Philadelphus. It was closely associated with the Mouseion, a research institute where scholars studied literature, mathematics, astronomy, medicine, and philosophy.
Ancient sources suggest the collection may have contained hundreds of thousands of scrolls, although the exact number is unknown and probably exaggerated in later accounts.
Julius Caesar's fire (48 BCE)
The best-known story involves Julius Caesar.
During his campaign in Alexandria in 48 BCE, Caesar ordered ships in the harbor to be burned to prevent them from falling into enemy hands. Ancient writers agree this caused a fire that spread beyond the docks.
The key question is: did it reach the Library?
- Caesar himself never mentions damaging the Library.
- Later writers, including Plutarch, say the fire destroyed the "great library."
- Other ancient authors instead mention warehouses containing books near the harbor being burned.
Many modern historians think the fire probably destroyed stored scrolls or a depot of books, but not necessarily the main library complex itself.
Evidence the Library survived Caesar
There are good reasons to think the institution continued after 48 BCE.
For example:
- Scholars are still recorded as working in Alexandria decades later.
- The geographer Strabo visited Alexandria around 20 BCE and described the Mouseion as still functioning.
- Later Roman emperors appear to have supported scholarship there.
This suggests that, even if Caesar's fire caused significant losses, it did not end the Library outright.
A gradual decline
Instead of one disaster, historians think several factors contributed over centuries:
- Political instability: The Ptolemaic kingdom ended, and Roman rule changed funding priorities.
- Reduced patronage: Maintaining a massive research institution required continuous royal or imperial support.
- Wars and civil unrest: Alexandria experienced repeated conflicts that likely damaged public buildings.
- Loss of copying: Ancient libraries survived by continually copying aging scrolls. Without investment, collections naturally shrank.
The destruction of the Serapeum
Another important event occurred in 391 CE.
The Serapeum of Alexandria, a temple complex that housed what may have been a "daughter library," was destroyed after Emperor Theodosius I ordered the closure of pagan temples.
It's debated whether many books still remained there. Some historians think the library collections had already dwindled significantly by this point.
The Arab conquest?
A famous story claims that when Arab forces captured Alexandria in 642 CE, the caliph ordered all the books burned because "if they agree with the Qur'an they are unnecessary; if they disagree they are dangerous."
Most historians reject this account because:
- it first appears about 600 years after the conquest;
- contemporary Arab and Byzantine sources do not mention it;
- it is generally regarded as a later legend.
What is the current consensus?
Most historians would summarize the evidence like this:
- Caesar probably caused a fire that destroyed some books, especially those stored near the harbor.
- The Library likely survived that event in some form.
- Its collections and institutions declined gradually over the following centuries because of changing politics, reduced funding, wars, and periodic destruction.
- By the late 4th or early 5th century, the great research library that had made Alexandria famous was probably no longer functioning as it once had.
So if you ask, "Who destroyed the Library of Alexandria?" the most accurate answer is: probably no single person did. Julius Caesar may have contributed to its losses, but the evidence points much more strongly toward a long process of decline and repeated damage than a single dramatic act of destruction.
