To some extent, it is. However, like many accounts based on real experiences, there could be elements of embellishment or interpretation to make it more engaging.
In the manga, Zero Two and Hiro have a different fate. They don't die. The plot takes them on a journey with various challenges but not to the point of death.
The 'bravo two zero' real story is about a military mission. It was a Special Air Service (SAS) operation in the Gulf War. A small team faced many challenges and difficulties during the mission in enemy territory.
I don't think it's a straightforward true story. Usually, such shows take liberties and combine various elements to make it more captivating. Maybe there are loose connections to reality, but it's not a pure retelling of actual events.
In the 'bravo two zero real story', the main characters were the soldiers of the Bravo Two Zero team. These were highly trained SAS operatives. Andy McNab was a prominent member among them. He later wrote about their experiences, which brought the story to a wide audience. They were all men who volunteered for a very dangerous mission behind enemy lines in the Gulf War.
I think the main theme of the story is the struggle between parental expectations and a child's own desires, along with the exploration of what it means to be successful in different contexts.