"This is a landmark ruling. It is the definitive case on Gulf War Syndrome to date," said Mark McGhee, the soldier's lawyer on Wednesday.
"This is going to have massive implications for hundreds of Gulf War veterans, who clearly suffer from Gulf War syndrome."
The army disputes the term "Gulf War Syndrome", an umbrella term for a number of illnesses, some serious, which have affected servicemen returning from Operation Desert Storm in 1991.
The Pensions Appeal Tribunal, which hears appeals from veterans who have had their claims for war pensions rejected, found that "veterans of the Gulf War later developed an excess of symptomatic ill health over and above that expected in the normal course of events".
They added: "The term Gulf War Syndrome is the appropriate medical label to be attached to this excess of symptoms and a useful umbrella for that label."
Ex-soldier Daniel Martin, 35, suffers from a variety of illnesses including joint pain, poor concentration and memory, asthma and chronic fatigue syndrome.
"The term Gulf War Syndrome is the appropriate medical label to be attached to this excess of symptoms and a useful umbrella for that label"
The Pensions Appeal Tribunal
Like other veterans, he blames cocktails of drugs prescribed by military doctors to protect against chemical attack, as well as exposure to depleted uranium munitions.
His battle with the Ministry of Defence (MoD) dates back to 2000.
"I have had to see so many doctors and been knocked down so many times by the MoD and Veterans Agency, I feel pleased now that a court of law looked at all the evidence and came up with the conclusion I have known all along," he said after the ruling on Monday.
The MoD has rejected the existence of Gulf War Syndrome for 14 years.
Some progress was made in September when for the first time they allowed the use of the expression as a "general term" but not as a "medical term".
Support groups say that 500 ex-British servicemen have died as a result of Gulf War Syndrome and another 6000 are still suffering from associated illnesses.
About 53,000 British soldiers took part in Desert Storm.