Okay - it seems I also need to learn some history - I am sure I had been told the version I gave on quite a reasonable authority (some kind of tv documentary many years back) but my memory may have erred. Your version checks out - thanks :)
You are partially right but have some major factual errors...July and August were not inserted, they were renamed. The original Roman months were Quintilis (5th month) and Sextilis (6th month) leading into September (7th Month) and so on through December. These months were renamed by Julius Caesar (Who was Pontifex Maximus at the time) when he did the calendar reform and by Augustus when he completed the calendar reforms to fully establish the Julian Calendar.
Originally, March was the first month of the year celebrating the god mars, followed by all the months leading to December (10th month) which completed the calendar. The Calendar reform added NOT July and August but actually added January and February. This is the act that misaligned the civil calendar with the month names. The Roman Religious calendar continued to list March as the first month of the year though for some time after this even though the civil calendar now had January and February as the first months.
So yes, months were inserted to misalign the month numbers with the names, but no to your statement that March was never the first month and that July/August were inserted.
You need to learn some history. March was never the first month. The reason Sept/Oct/Nov/Dec are named so is because there used to be only 10 months until the addition of July and August, named after two leading roman figures of the time, one a proconsul during the republican civil war, Gaius Julius Ceasar (hence July,) and Gaius Julius Ceasar Octavius, who took upon himself the name "Augustus" (hence August) after he was named first emperor. Thus the months named by their position after that became obsolete.