The failed coup of July 15 left the Turkish army humiliated and weakened at a time when it must tackle the twin challenges of fighting guerrillas of the Kurdistan Workers' Party (PKK) and jihadists from the Islamic State (IS) group.

Its future will partly be decided on Thursday at a meeting of the Supreme Military Council in Ankara, which Turkish media have said could force through a "historic" transformation in the armed forces.

In a sign of the army's weaker post-coup status, the meeting will be held at the Cankaya Palace of the Turkish premier and not as in the past at military headquarters.

What now for the army?

With 750,000 men, mostly conscripts, Turkey's army is the second largest force in the NATO military alliance.

Until 2010, the constitution made it "the guardian of the Republic of Turkey" and the country's secularism. A bygone prestige, with more than 3,000 soldiers now arrested for taking part in the coup.

Today, close to a third of the army's generals -- 143 -- have been remanded in custody, in an unprecedented purge under President Recep Tayyip Erdogan.

For Sinan Ulgen, chairman of the Istanbul-based Centre for Economics and Foreign Policy Studies, "the botched coup will have repercussions on Turkey's ability to contribute to regional security".

Along with the affect on army morale, "weakened trust" following the coup will make cooperation between police, military and intelligence services "particularly problematic," Ulgen wrote.

The government has already announced the gendarmerie, which looks after domestic security, and coastguard will now be under control of the interior ministry, in a huge blow to the army's powers.

Francois Heisbourg, at the International Institute for Strategic Studies, said the episode would "confirm the removal of the army" from the political arena, while Erdogan's capacity to motivate the army would be "weak".

But the purge will open the field "to unexpected promotions, which is very motivating". These new cadres will make their mark "in a matter of months rather than years," the researcher told AFP.

What consequences for the battle with IS?

Since last year US air force bombers have taken off from the Incirlik base in southern Turkey to pound jihadists in Syria.

But electricity at the base was cut off after the attempted coup, forcing the Americans to use their generators.

Incirlik was a key point in the failed putsch and its commander, General Bekir Ercan Van, was arrested.

For Stephen Biddle, at the Council on Foreign Relations based in Washington, Incirlik is "not decisive for the campaign" against the IS group.

"It makes US air strikes cheaper and more efficient, but we can reach Syrian targets from other bases if we need to," he said, adding that ensuring proper security on Turkey's border with Syria was more important.

A blow to anti-PKK fight?

Hostilities resumed a year ago in Turkey's southeast against the separatist Kurdistan Workers' Party (PKK), claiming the lives of nearly 500 members of the security forces.

General Adem Huduti, commander of the second army in charge of this counter-insurgency, must now be replaced as he is behind bars.

"The shakeup looks set to impinge Turkey's ability to fight the PKK," says Lale Sariibrahimoglu of Jane's Defence Weekly.

But "most of the fighting is done by the gendarmerie", said Bulent Aliriza, at the US-based Centre for Strategic and International Studies.

"It's too early to tell" the consequences of this reorganisation, said Aliriza. And it will be difficult to detect from the outside given the institution's opacity.

Does Turkey remain a reliable ally?

The response of Ankara to the putsch has "raised questions about Turkey's reliability as an ally," said Marc Pierini, former EU ambassador to Ankara and visiting scholar at the Carnegie Europe think-tank.

Many regular Turkish interlocutors for the Americans and NATO forces are today in detention.

After the night of chaos and in the acrimonious context with Ankara, US officials "cannot not ask" the question of what to do with their nuclear warheads stored at Incirlik, said Heisbourg.

But moving them would again damage relations with the Turks.

These doubts about Turkey, a member of NATO since 1952, are not new -- but they are reinforced amid tensions between the West and Russia.

Yet after several frosty months, relations between Ankara and Moscow are warming: Erdogan is scheduled to meet his counterpart Vladimir Putin in Russia in early August.

Bruno Tertrais at the Foundation for Strategic Research, based in Paris, said a break with NATO "would not be to Ankara's advantage, but Erdogan is capable of decisions that have little rationality".