Hello,
I am not sure if this workflow would work with that version of ArcGIS Enterprise. It not supported using ArcMap.
Because the ArcGIS API for JavaScript 4.x includes support for the Dictionary Renderer, you can use ArcGIS Pro to publish the Military Overlay created by the Military Symbol Editor as a feature layer (Share as Web Layer). Rendering of the features using the dictionary renderer is happening on the client.
Before you publish, you need to update the dictionary renderer for each layer in the Military Overlay to use the associated web style. By default, the Military Symbol Editor will use the desktop style for the military symbol dictionaries, which are installed with ArcGIS Pro.
To choose a web style instead, in the Dictionary Renderer on the Symbology Pane, you can click the More drop-down menu and then click Add custom dictionary to browse to a web style to add to the dictionary to the list. If you have a connection to ArcGIS Online, you can search for the style based on the standard name ("MIL-STD-2525B").
If you do not have a connection to ArcGIS Online, you can share a desktop style as a web style in ArcGIS Enterprise. To do that, click the More drop-down menu and then click Add dictionary to project. This will add the currently selected dictionary in the drop-down list to the list of Styles in the Catalog pane. Then you can right-click on the style in the Catalog Pane and choose Share As Web Style, which will create a new portal item for the web style. At this point, you should be able to browse to that web style as described in the previous paragraph.
The other thing you need to do before you publish is remove any group layers from the Table of Contents, since they are not supported in web feature layers.
Let me know if you have any more questions.
-Kerry