A static public IPv4 address is required so people can actually connect to your wargame server. Usually, your provider assigns you a new IPv4 address from time to time. You can check this by doing the following:
1) Go to some site like whatismyip.com and note down your IP address. Note, we are talking about your external IP address here. If your computer is sitting behind a router, there is also an internal address, most likely 192.168.0.XXX.
2) Restart your router.
3) Re-do step one and compare your IP with the one you noted before. If you do have the same, you might (not necessarily) have a static IP.
Another way to check is by calling your provider. Also, your provider may offer you a static IPv4 address if you request so.
Why is a static IPv4 address required?
Because if the IPv4 address changes, people will no longer be able to connect to your server.
This sounds like a static IP is a must-have, but first let's look at two usecases:
1) You want to have a wargame server running 24/7 regardless of you being around or not. Well, then you will need a static IPv4 address. Rather, you will need a server (look for "rent virtual private server") which is running all the time and which has a static IPv4 address so people can connect to it. This is not so easy because you need to administrate your server and secure/harden it (or it will get hacked immediately).
2) You want to run a wargame server which is available when you play. That's easy to do, your home computer is sufficient. Look around, there are guides on how to setup this by using VirtualBox (for example the Steam guide I've linked to in L@nge's post or the docker guide here). You do not need a static IPv4 address, you just need to adjust the server settings every time your IP address changes. This is quite easy to do.
Therefore, it may be unnecessary to acquire a static IP address, depending on what you want to do.
Note, this is no official recommendation to ignore Eugen's requirements. I'm just pointing out that a static IP will not make any difference if you launch your wargame server only when you are playing and shut it down once you're finished.