A problem occurred running the Server launcher.java.lang.reflect.InvocationTargetException
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
        at java.lang.reflect.Method.invoke(Unknown Source)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.run(ServerLaunchWrapper.java:70)
        at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main(ServerLaunchWrapper.java:34)
Caused by: java.lang.NoClassDefFoundError: org/apache/logging/log4j/Level
        at net.minecraft.launchwrapper.Launch.launch(Launch.java:94)
        at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
        ... 6 more
Caused by: java.lang.ClassNotFoundException: org.apache.logging.log4j.Level
        at java.net.URLClassLoader.findClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
        at java.lang.ClassLoader.loadClass(Unknown Source)
        ... 8 more

 

Keeps popping up when I try to run the forge-1.12.2-14.23.5.2854.jar with my start.bat file. The code I used for the start.bat is shown below:
 

java -Xmx6G -jar forge-1.12.2-14.23.5.2854.jar
PAUSE

1.12 is no longer supported on this forum.

Please update to a modern version of Minecraft to receive support.