If this is a very important application in your company that is expected to last several years, then I would suggest start small. Start looking for little pieces that you can test or test with small modifications to the code to make it testable.
You should look into integration test runners like Cucumber or Fitnesse. Depending on your scenario, an integration test runner will either act as a client to your server and make the appropriate calls into the server, or it will share some domain code with your existing client and run that code. You will give your scenarios a sequence of calls that should be made and verify that the correct results are output.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.