Persuasive writing is a form of building logical arguments along with the emotional appeal. It helps in molding the reader's point of view as per the thoughts of the writer. Valid information is added and the argument is present in the way that it influences the reader.
In the given message, the writer had used the technique of being reasonable and specific. He had presented his problem in a subtle manner along with the proper solution to it.
Queen Elizabeth’s purpose in this passage is to rally her troops up and ready them for war, and convince them that she is fit to lead them even though she is a woman and she will fight alongside them to prove it.