Part of the Ai to Yomei no Tame ni Series (愛と名誉のためにシリーズ), also called the "Love and Glory" series, which goes as follows:

1. Kono Ai wa Kizutsukanai
2. Tsubasa o Oranaide
3. Eikyuu no Kikan
4. Kono Yoru ga Aketara

from fictiondb:
Marine captain Morgan Trayhern couldn't risk staying in the States, yet he didn't dare leave. Fragile, gutsy Laura Bennett had been injured saving his worthless skin, and a Trayhern never dodged duty. Despite the danger, he had to protect his sweet guardian angel. To his surprise, Laura's bulldog stubbornness matched his own, and her love implored him to unearth what he thought he'd forever buried on that bloody hill seven years ago. But once he faced his entire past, could he ever count on a future?