Before F.R.O.N.D.E.R: Epilogue

A US Marine and two other US Soldiers got to another world when they were working on an operation, caused by the strangeness of the location's phenomenon. They got there. These modern military personnel shortly managed to make progress in that world, and become the Lords of a Kingdom named Warsaw.
However, that Kingdom's about to have a war... 

This story's available on Wattpad, Scribblehub, Royal Road, Webnovel and the newly added app Inkitt.