Installing Windows 10 to an External Hard Drive SSD I have a 2016 MacBook Pro, with Touch Bar, running macOS Sierra (10.12.2). I am trying to install Windows 10 to a new external SSD using Boot Camp Assistant. 

I have read numerous methods detailing how to complete this installation, including this great thread. 

Under macOS Sierra, this seems to be different. For example, when I run Boot Camp Assistant in macOS Sierra, the first screen is the standard introduction screen, and the second screen jumps right into the partition screen. I have no ability to download any software, or even to select my target drive. 



This is as far as I have gone because I do not want to modify the partition of my internal drive. 

Also, here is a screenshot of Disk Utility where you can see my external SSD currently partitioned and ready. I am wanting to install Windows 10 on the 100GB W10 partition (MS-DOS). The drive is plugged in, but Boot Camp Assistant does not recognize it (or allow me to select it as an install destination). 



Any ideas?

Update 1: 
I tried to get around this problem by trying to ignore Boot Camp Assistant altogether and just installing WindowsToGo on my SSD. 
No luck. I eventually thought the problem might be because the SSD is split in 2 partitions, and maybe Mac doesn't like that. So I wiped the whole drive and installed WindowsToGo on the single partition using this guide. Everything appeared to install fine, but the MacBook will not recognize the drive when booting. 

Update 2: 
I thought I might be doing something wrong, so I tried using AAOMEI Partition Assistant Standard (which automates the WindowsToGo installation). Same problem. Everything on the drive looks fine, but the Mac won't recognize it as a bootable drive.
It seems to be a bug (or feature) in 10.12.2 that macOS will not recognize an external SSD when booting.

I have installed Win10 via WindowsToGo several months ago on an external SSD, when my macOS version is 10.11. Everything was fine when I upgraded to 10.12 and 10.12.1, but at the stage of 10.12.2, the external disk cannot be recognized anymore during booting.

At current no solution is provided by Apple. I suggest that you roll back to 10.12.1 or earlier versions if you are eager to do the installation.

EDIT: I happened to boot the external SSD successfully several times for 10.12.2 by cutting off all the network connections (wireless and ethernet).