Several people have contributed to the completion of this PhD thesis, and I would like to express my gratitude to them. First, thanks to all of the contributors and participants in the Royal Norwegian Navy. Ragnar Vaernes at Falc Nutec, for stimulating my interest in operational research. My main supervisor Dr. Olav Kjellevold Olsen, without whom this project never would have seen the light of day. Thank you for the guidance, trust, thoughtful discussions, and showing me how to thrive as an academic. My co-supervisor and somnologist par excellence, Professor Ståle Pallesen. My other co-supervisor Dr. Roar Espevik for his hands-on contributions to the data collection and discussions, and Dr. Jørn Hetland for introducing me to shortitudinal multi-level analysis. I would also like to thank my family for all their support. I also wish to thank Sondre Aasen Nilsen for all the therapeutic debriefings. Lastly, a special thanks to Veronica for making me more resilient. Thanks for all the love.