Turkey's president is making a Machiavellian move
But Turkey's access came with conditions.
Ankara is clearly is more concerned about its sizable and rebellious Kurdish minority, which is upwards of 13% of the country's population, than it is about ISIS, which the Turkish government has been consistently accused of supporting.
And providing the US access to Incirlik gives the Turks more freedom to strike the Kurds in Iraq, which they began doing right after announcing the agreement with the US.
It's unclear if the quid-pro-quo will be worth it. In any case, it will almost certainly meant to work for Turkish president Recip Tayyip Erdogan's political advantage.
Erdogan's gambit
After the reproted agreement, Turkey struck against both ISIS in Syria and the Kurdish PKK stationed in northern Iraq.
Turkey also cracked down on alleged terrorists within its orders in a massive string of arrests - with the majority of those arrested belonging to the PKK.
The decision to strike at both ISIS and the PKK - the perennial enemy of the Turkish state that's waged an insurgency since the 1980s, driving a conflict that's killed many as 30,000 people - is a Machiavellian move by Erdogan.
Turkey's internal politics are having a big impact on the fight against ISIS, and the US might now be ensared in the Turkish strong-man's latest power play.
Peace no longer politically useful
During June elections, Erdogan's ruling Justice and Development Party (AKP) lost its parliamentary majority for the first time since 2002.
The success of the HDP limited Erdogan's own political ambitions of empowering the presidency of the country at the expense of the parliament.
The success of the HDP has also led to a fracturing of the Turkish parliament, as currently no party holds a majority and coalition talks between the AKP and other have faltered.
Erdogan's government has been attempting to negotiate a fragile peace process since 2012, and the AKP rode to power partly on its ability to capture segments the Kurdish vote.
However, it seems the peace process and the Kurds are no longer politically useful: On July 30th, the leader of Turkey's ultranationalist Nationalist Movement Party (MHP) said he would be willing to form a coalition with the AKP if the peace process with the Kurds were formally ended.
Erdogan 'will not allow PKK to abuse the political space'
The PKK are a Kurdish separatist group, originally inspired by Marxism, that has been designated a terrorist organization by Turkey, the US, and the EU for their attacks against military and non-military targets.
An end to the peace process would likely lead to more violence, and could lead to the PKK once against starting its insurgency in the east of Turkey.
But Erdogan would also be able to form a majority in parliament with the MHP, thereby sidelining the Kurdish political party and the center-left Republicn People's Party (CHP).
To further limit the influence of Kurds in Turkish politics, Erdogan has also threatened to strip members of parliament of diplomatic immunity and prosecute them for ties to the PKK. The threat is obviously aimed at the HDP.
"The underlying strategy is to coerce the HDP to physically renounce what the PKK is doing," Aaron Stein, a non-resident fellow at the Atlantic Council's Rafik Hariri Center for the Middle East, told the Huffington Post.
Erdogan wants to turn the public against the HDP, shore up support among conservatives in Turkey, and rule with total authority despite the loss of his majority in parliament.
"The campaign against ISIS is a long-term campaign, possibly for years - as long as ISIS is not eliminated," Sinan Ulgen, a former Turkish diplomat, told the Wall Street Journal. "The strikes against PKK are more intense today but they are likely to be short-lived.
"They're a signal by Turkey that it will not allow PKK to abuse the political space created by the Kurdish settlement talks."
Consequences for the US
Any prolonged concerted effort by Turkey against the PKK will only further complicate an already tangled web of alliances in the fight against ISIS.
In addition to bombing the Kurds in northern Iraq, the YPG - a Syrian Kurdish militia aligned with the PKK - has accused Ankara of shelling a Kurdish-held village in northern Syria.
While Ankrara denies that claim, tensions will continue to simmer and explode throughout Kurdish-held regions as long as Turkey continues to battle both the Kurds and ISIS.
And since the US views the YPG as the most capable force currently deployed on the ground against ISIS, any Turkish hostility against the YPG or the Kurds more generally will be a glaring contradiction within the anti-ISIS forces.
An unnamed US official told Foreign Policy on Tuesday that due to the YPG's successes against ISIS, the US views them as an important regional partner.
"We don't want to see that [relationship] complicated in any way" and "we are not going to forsake them," the official said to Foreign Policy.
But Turkey has a different view of both the Kurds and its own interests in the region and just gained a freer hand as the result of its deal with the US.
Conseqeutnly, continued US support for the YPG makes things awkward.
On Thursday, State Department Deputy Spokesperson Mark Toner pledged that US aircraft operating out of Incirlik Airbase will continue to provide air support with the YPG. But Toner's comments came just a day after the Turkish Foreign Ministry said that any air support missions for the YPG were not included in the US-Turkey deal.
Basically, Turkey and the US are attempting to harmonize their approach to the war against ISIS but don't agree on how or whether the Kurds fit into such a struggle.
For now, the US has to find a way to strike a middle approach that will satisfy both the Syrian Kurds and an ever uneasy Erdogan - or else the anti-ISIS campaign may pay a steep price for US access to a single Turkish airbase.