Transact SQL :: Sorting By Minimum Of Multiple DATETIME Columns

I have a view in my database detailing the expiry date of each credential for each employee. The view is designed as to display one record per employee and in that record is the expiry date of each credential and the days remaining. So the columns are as follows:-

Employee CodeExpiry Date (x8 columns) (named as credential e.g. [Passport])
Days Remaining (x8 columns) (named as "TS_" + Credential)

I'm trying to use the CASE function to compare each DATETIME column with one another and retrieve the minimum. How can I return the minimum date as a run-time column and sort the view by this column? My code is as follows:-

SELECT [Passport],[TS_Passport],[Visa],[TS_Visa],[Civil_ID],[TS_Civil_ID],[KOC_Pass],[TS_KOC_Pass],[JO_Pass],[TS_JO_Pass],
[Ratqa_Pass],[TS_Ratqa_Pass],[Driving_License],[TS_Driving_License],[Health_Book],[TS_Health_Book], CASE
WHEN Passport <= Visa AND Passport <= Civil_ID AND Passport <= KOC_Pass AND Passport <= JO_Pass AND

[code]....

I've been told that this is the most efficient given the number of records in my database. The Min_Date is always NULL. I need the minimum of the 8 dates to be the Min_Date.