Is he considered a martyr, one who died while a soldier in one of these situations: during training, or during special guard duty?

Whoever dies a natural death is not considered a martyr, unless they patiently endure in the land of jihad, sincerely seeking martyrdom. In this case, it is hoped that Allah will grant them the reward of martyrs, even if they die in their bed, because the Prophet, peace and blessings be upon him, said: "Whoever sincerely asks Allah for martyrdom, Allah will make him reach the ranks of the martyrs, even if he dies on his bed."