Deby, a 68-year-old general who came to power in 1990, was given the honour by the National Assembly, where his party holds a strong majority, after he led an offensive against jihadists in April.

"You are an icon and a symbol for Chad," said assembly speaker Haroun Kabadi.

Deby, clad in ceremonial regalia, said the prestigious military rank was awarded for a "feat of arms" and he dedicated the tribute "to all my brothers in arms".

"The threat of terrorism is still there, and it is ruthless," he warned.

"The fight against terrorism is a vital imperative and will remain at the core of our concerns."

The offensive was launched after Boko Haram jihadists killed nearly 100 troops in March at a base at Bohoma in the west of the vast arid country.

Bohoma is located in the Lake Chad region, which straddles the borders of Nigeria, Chad, Cameroon and Niger and has become a haven for jihadists who hole up on islands in its marshes.

The toll was the biggest one-day loss in the history of Chad's armed forces, and many commentators saw it as a humiliation for a country which prides itself on its military strength in the Sahel.

The counter-attack, named "Wrath of Bohoma", forced out every jihadist from Chad, Deby claimed afterwards.

However, on Saturday, he acknowledged that Boko Haram "will still do a lot of harm" to Chad in cross-border attacks.

- Military nuance -

Deby struck a martial tone during his speech, and there was barely a reference to the anniversary or Chad's history -- an approach criticised by the opposition.

Saleh Kebzabo, a veteran opposition leader and former presidential election challenger, said "independence day has been reduced to a mere ceremony, of 'present arms'."

Chadian political analyst Evariste Ngarlem Tolde said, "the rise to independence will never be retold to this country's children and grandchildren, because this crucial event will have been eclipsed by the promotion to the rank of marshal."

The country today known as Chad had a thousand-year history of kingdoms and empires before French colonial forces took over after a battle in 1900.

After World War II, political parties began to sprout, adding to the momentum that led to independence from France in 1960, with Francois Tombalbaye as the state's first president.

But Chad has had a post-independence history of chronic instability, marked by coups and accusations of election fraud, as well as grinding poverty.

Deby himself took power in 1990 by overthrowing his former boss, the authoritarian Hissene Habre, whom he once served as military advisor.

In the West, though, he has gained much support, especially from France, for his commitment to fighting jihadism.

"I will continue to be the first guarantor of the freedom of my fellow citizens," Deby said on Tuesday.

He also released 538 prisoners as part of the independence day commemorations.

They include General Abdelkader Baba Ladde, a Chadian rebel who had been active in neighbouring Central African Republic (CAR).

He had been sentenced last December to eight years on charges of illegal possession of weapons, criminal association, rape and arson.

UN troops arrested Ladde in CAR in December 2014 and he was extradited to Chad in January 2015.