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In the Star Trek reboot movie, Nero's ship the Narada was a mining ship. However, it was very heavily armed with devastating weaponry that far outmatched any ships from the earlier time. While the Romulans are a warlike race and a mining ship may need to defend itself against pirates or the like, the sheer level of offensive weaponry on the Narada seems very out of place on a civilian vessel*. The fact that the ship has decades newer technology doesn't really explain just how well armed it is.
If I understand the timeline, the Narada encountered Spock's Vulcan ship just as it had failed to prevent the destruction of Romulus, which would have given no opportunity to arm itself beyond what it was already provisioned with.
So my question is, What canon reason would there be for the Narada to be carrying such extensive weaponry when it is a mining ship?
* In my head I pronounced this as "wessel" in honour of Chekov :)