1920 was a bad year for Cork. Well, a bad year for Ireland. But this is about what happened in Cork.
Ireland was fighting the British for its independence and the fighting in Cork was intense. The Burning of Cork by Gerry White and Brendan O’Shea is a rather detailed account of that fighting.
I found the book a bit too detailed for me so I just skimmed it. But there is certainly a lot of information here, including appendices and references.
The violence escalated significantly during that year with Irish republicans attacking crown forces and crown forces attacking the Irish. And retaliation and escalation ultimately resulting in the burning of large parts of Cork.
The Burning of Cork is a detailed account with both testimony of eye witnesses and testimony before Parliament. There was also a documentary of the same name.
At least part of the book is available online courtesy of Google. Or you could seek out the full book or documentary.