I'll give you an easy step for Inkspace!
1. New Document in Inkspace!
2. Draw big polygons of your map you're drawing!
3. Draw a line to separate the polygon into territories!
4. Click the line and the polygon and press Ctrl+/ or Path>Difference
5. Finished work.
6a. That ugly overlap though.
6b. Border overlap each other? Go to File>Inkspace Preferences
6c. Now go to Steps and click on Inset/Offsets and set the value to 0.5!
7. Click on all of the territories and Ctrl+Shift+9!
8. Border now overlap less and attempts to touch other.
9. Now you have perfect touching border but be careful to not use that magic Ctrl+Shift+9 too much. Otherwise, the territories are going to look overdosed.
10. Glory to Warlight!