Not five minutes after I posted Earnest Student's grade on the final, I got an email.
Dear Picky Historian,
I am really really disappointed in my grade. I worked really really hard on that paper, and when I saw so many points off for not having an argument I was really annoyed. You never told us we had to have an argument and it was not in the assignment instructions. Please reconsider the grade.
Sincerely, Earnest Student.
Dear Earnest Student,
I am sorry that you are disappointed in your grade. However, the grade will stand. The assignment instructions ask you to defend your assessment of why and how event X happened. That requires having an argument, by definition. Furthermore, every time any student, including you, asked about the paper format, I mentioned "leading with your argument" and "must have an argument." The next class, please do not talk loudly to your classmate or rabbithole on your laptop while I am discussing paper instructions.