Start with a simple line segment.
Clipboard01.jpg
Then convert the points and pull the arms to create the curves you want.
Clipboard02.jpg
Duplicate that path. Then go to edit>transform path>scale. once there the flip horizontal option will be available.
Clipboard03.jpg
Now copy that path. Go back to your first path and paste in the 2nd path.
Clipboard04.jpg
Now you have one full path of that shield shape.
If you want additional lines in there just do those before you duplicate. It's pretty quick to do.