Prince Harry and Meghan Markle were left "shocked" to their core by stories they heard from military veterans during a private fact-finding visit to Colchester Garrison, the royal has revealed.
Giving a keynote speech to a conference about veterans' mental health, Harry, who served as an Army officer for 10 years, also said he witnessed the suffering of those around him "struggling to seek out the help they desperately need".
Harry and fiancee Meghan recently visited the garrison to learn more about the North Essex Veterans Mental Health Network, a collaboration between the NHS, Ministry of Defence and Third Sector, and met veterans, health professionals and other staff.
The Prince, who arrived an hour before he was due to speak to hear experts address the delegates at King's College London's Strand Campus, said:
"I have seen those I have served with suffer, struggling to seek out the help they desperately need. And we know there are more just like them who continue to suffer in silence.
"And when the individual doesn't or can't reach out for help, it is also their families who suffer; especially their spouses and children, who are left feeling desperate and confused as they try to seek appropriate help for the ones they love."
Harry served two tours of Afghanistan - first as a forward air controller, then as an Apache pilot - and went on to support the rehabilitation of wounded veterans and serving personnel most notably through his Invictus Games.
He added: "Some of the stories Meghan and I heard when we visited Colchester Garrison a few weeks ago shocked us to our core.
"But despite meeting these people and others who are in the darkest of places, I am continually surrounded and inspired by amazingly positive outcomes."
Harry said through his charitable support of veterans and the Invictus Games, he had been "privileged to witness the journey that many men and women have taken - from desperation and isolation, to amazing achievements, regaining self-worth, and finding community once more".
But he urged medical professionals, charity workers and other groups to help veterans in need of support "by sharing best practice, sharing resources, and helping each other to improve access".
He added: "In spite of this progress, accessing help is still a confusing marketplace.
"The veterans should always be our number one concern, allowing us to put aside our individual brands or publicity, for their sake."
Harry went on to try and dispel the "misconception" that mental health is the main issue veterans face with post-traumatic stress disorder (PTSD) the lead problem, with secondary effects of extensive substance misuse, unemployment and homelessness.
He said: "In reality, just 2.4% of those people leaving the forces in the last three years were medically discharged because of mental health, and just 0.9% because of post-traumatic stress.
"As a recent Kings' study shows us, the proportion of veterans diagnosed with post-traumatic stress is very similar to the general population, with just 1.6% separating them."
He told the conference that veterans were a valuable resource:
"Military service is enriching and good for society. Our experiences show that employers value veterans and we want to push that message that they are incredible assets to any business.
"Any employer would be lucky to have them as part of your team - and that's a fact.
"Serving your country makes you a better person for your family, community and country; increased confidence, discipline, teamwork, loyalty, and the ability to realise huge potential in yourself."