Vang Pao, the former general and leader of his Hmong ethnic group in Laos, has died in exile in the US, aged 81.
He had been in hospital for about 10 days before his death late on Thursday.
As a young man, he had fought against the Japanese during World War II, and with the French against the North Vietnamese in the 1950s.
He led a 15-year CIA-sponsored secret war in Laos during the Vietnam War and, when it was lost, led tens of thousands of his people into exile.
Thousands of ethnic Hmong are expected to attend his funeral in Fresno, California.
"He'll be remembered as a great general, a great warrior, a great Hmong soldier," his friend Charlie Waters told AFP news agency.
However the response from the Laos government was muted. "He was an ordinary person, so we do not have any reaction," a government spokesman was quoted by AFP as saying.
'Last of his kind'
Gen Pao was a controversial figure, deeply loved by many Hmong - an ethnic minority in Lao that complains of persecution - for his insistence on freedom from foreign domination.
Former Central Intelligence Agency chief William Colby once called Gen Pao "the biggest hero of the Vietnam War".
But critics say that by allying himself with the US, Gen Pao caused his people untold suffering - something that he himself recognised.
"I lost 17,000 men, almost 10% of the total Hmong population. The Hmong sacrificed the most in the war and were the ones who suffered the most," he said at the Heritage Foundation think tank in 1987.
Americans who first came into contact with him found a man skilled in warfare and with the charisma necessary to sustain a dangerous, 15-year operation in support of the US against the North Vietnamese.
The CIA airline, Air America, carried Gen Pao and his fighters across the country.
On the ground, he and his men disrupted Vietnamese supply lines and engaged in pitched battles to try to stave off the Vietnamese-backed communist victory in Laos.
When that effort failed in 1975, Gen Pao led many thousands of Hmong into what are now well-established exile communities in the US.
The Central Valley of California, Minneapolis and cities throughout Wisconsin have a Hmong presence of an estimated 30,000-40,0000.
In his later years, Gen Pao was accused of leading rebellions or sponsoring subversion against the People's Democratic Republic of Laos.
In 2007, he was charged along with nine others with plotting to use AK-47 rifles, missiles and mercenaries to overthrow the Lao government. Charges against him were later dropped.
He was regarded by some as an exiled head of state.
"He's the last of his kind, the last of the leadership that carries that reverence that everyone holds dear," said Blong Xiong, a Fresno city councilman and prominent Hmong-American.
"Whether they're young or old, they hear his name, there's the respect that goes with it."
BBC News website readers have been sending in their reaction to the news. Here is a selection of their comments.
General Vang Pao is our greatest leader and will remain this way. He was our beacon of hope and is the very reason why we are here in the US, our land of opportunity. He will forever be missed and no one will be able to replace him in our hearts, mind and community. He was a much loved leader that led his people. He wasn't one to be above anyone, but rolled up his sleeves and challenged our everyday struggles with us. He is a great hero that - even though was considered "exiled" - was truly not because his people followed him to the very end. Mao Lee, Fresno, California, US
I cannot believe that there can be any celebration of someone who supported the US and the CIA in Vietnam/Laos. Your note that as a Community Leader he worked as a security guard at a supermarket in the USA says it all. The US should still be damned for the horror that they exercised on Vietnamese (and US) people in the Vietnam war - and in Laos and Cambodia. Mike, Cape Town
It's a tragic loss for the Hmong community. A historic Hmong leader has passed away. Neng Vang, St Paul, Minnesota, US
General Vang Pao will always be regarded as the Hmong people's saviour of the war. He negotiated our freedom from what would be certain death for many of us in Laos. It is too bad that young people, like me, will never fully understand the extent of his courage, and the charismatic nature of this man. I just wished that he had done more for the young people here in the US. Maybe now that the only "leader" we have known is gone, maybe the Hmong community can finally understand that a divided community is not as strong as one that is unified. I certainly hope his death will cause unification and not further separation. Gregory Yang, Merced, CA, US
I met Vang Pao once in the refugee camp at Loei when he and Jerry Daniels were engineering the translocation of the entire tribe to America against the wishes of Congress. The visionary leadership at that point has become, and deserves to be, legendary. He could have just joined his relatives in Missoula but he stayed and engineered the future of hundreds of thousands of his people with craft and brilliance. With Jerry dead in 1984, the Hmong people have lost the last of the pair which worked together and alone created their destiny. I feel so proud to have met a man of his stature, may he be at peace in the presence of the Lord. Dan Pride, I.C.E.M Evacuation Officer Ampur Loei
As we heard the news, my parents were crying. They couldn't sleep last night and they told me that they don't know what is going to happen to the Hmong people now that General Vang Pao is gone. He has been the father figure for the Hmong people and this is going to be a very hard time for our community. Our community leaders will meet together and get this funeral done first and then we will talk about what we are going to do next. Pao, St. Paul, MN, US
General Pao was the last of the Nationalist leaders from the Vietnam era. Men like him fought the Japanese and anyone else that wanted to dominate their country. We, in the US, could not tell the difference between a nationalist and a Communist. So we supported Catholics to rule a country of non-Catholics and other such stupidities. General Pao and the loyalty of his people is a good story with a semi-tragic ending in that most are far from home, the worst hell on earth for a nationalist. Mike Reid, Sheridan, Oregon, US