Frida Ghitis is a world affairs columnist for the Miami Herald and World Politics Review and a former CNN producer and correspondent. Follow her @FridaGhitis . The opinions expressed in this commentary are solely those of the author.

(CNN) The new details emerging about the threat of ISIS, including the possible use of chemical weapons and the systematic rape of young girls , are dreadful.

But another disturbing development has surfaced: The United States appears to have undercut -- perhaps even betrayed -- Kurdish militias, the only truly effective fighting force so far in the war against ISIS.

The Kurds are now coming under attack not only from ISIS but also from Turkey, a U.S. ally.

The decision may have also been influenced by political considerations, as Turkish President Recep Tayyip Erdogan tries to weaken a Kurdish political party ahead of likely elections in the coming weeks

For decades, Turkey has battled Kurdish efforts to create an independent state. The battle for independence was spearheaded in Turkey by the PKK, the Kurdistan Workers' Party, branded as a terrorist organization by the United States and others. The PKK and Turkey had carried out a peace process since 2012. But, amid mounting attacks and counterattacks, including the killing by the PKK of several Turkish police officers, Erdogan says the peace process is now dead.

The PKK is linked with some of the United States' closest allies against ISIS, including the YPG militias that defeated ISIS in places like Kobani in Syria, one of the few battlefield victories against ISIS.

As Syria's Kurds have expanded their territorial gains in Kobani and other areas near the Turkish border, authorities in Turkey have grown increasingly nervous. Government critics say that is the real reason why Erdogan decided to join fight against ISIS , as a cover to prevent Kurdish territorial unity.

The United States had spent many months trying to convince Erdogan to join the fight against ISIS; to close the borders to people joining ISIS via Turkey and to do more to help the mission. Erdogan had refused, amid raging rumors that Turkey, a NATO member, was in fact helping ISIS.

But then came a turning point. On July 22, President Erdogan and President Obama had a telephone conversation one day after a terrorist massacre in Suruc, Turkey, that killed 32 people. Authorities blamed ISIS. But many Kurds said the government was at least partially responsible. The PKK killed several policemen in retaliation for Suruc.

Suddenly, Erdogan spoke with Obama and announced he would join the fight against ISIS. U.S. and coalition aircraft started using Turkish air bases at Incirlik and Diyarbakir, much closer to their bombing targets. Turkish fighters were set to join the campaign.

On the surface it was progress. The reality on the ground was very different.

Turkish bombing raids, which were supposed to target ISIS, went mostly against Kurdish positions. The Kurds protested. Even the YPG, the victors of Kobani, said they came under Turkish fire inside Syria. Turkey denied it.

In Iraq, the government was furious. If Turkey had attacked ISIS, which has captured Iraqi territory, the reaction would have been different. Instead, Iraqi Prime Minister Haider al-Abadi called the attacks against Kurdish bases "an assault on Iraqi sovereignty."

The new Turkish campaign was also supposed to stop ISIS operations inside Turkey. Authorities unfurled a domestic dragnet that Turkish Prime Minister Ahmet Davutoglut described as a "synchronized fight against terror." Security forces detained 1,302 people. But only 137 of them were thought to have links with ISIS. The vast majority, the government admitted , were suspected of links with the PKK.

While Turkey has unleashed its forces against the Kurds under the pretext of helping the United States and its anti-ISIS coalition, officials in Washington have remained rather restrained in its response. The State Department says it's a "coincidence" that the onslaught against the Kurds comes after Turkey agreed to work with the United States on ISIS.

"There's no connection between what they did against PKK and what we're going to try to do together against ISIL," said spokesman John Kirby, adding that Turkey has a right to defend itself against terrorists.

Privately, one U.S. military official said that Turkey tricked the United States and is using the anti-ISIS coalition as a cover.

"Turkey wanted to move against the PKK, but it needed a hook," an unnamed senior military official told the Wall Street Journal.

Whether the telephone conversation between Obama and Erdogan included discussion about how much latitude Turkey would have in hitting Kurdish targets is unknown. But it seems like in the three weeks since then Turkey has struck the enemies of ISIS much more fiercely than it has hit ISIS.

Erdogan's critics at home see another thinly concealed motive. Erdogan was hoping that his AKP would win a big majority when Turkish voters went to the polls in June to elect a new parliament. That would have allowed him to push for constitutional changes to make the presidency, and himself, much more powerful. Instead, a small Kurdish party, the HDP, stunned by winning 13% of the vote, tilting the balance and depriving the AKP from winning a majority for the first time since 2002.

Negotiations to form a coalition government look set to fail, which would mean snap elections; another chance for Erdogan, the most powerful politician Turkey has seen in decades, to win his coveted majority and have the parliament write a constitution with a presidential system.

By ending the peace process with the Kurds and inflaming the fight with the PKK, Erdogan is helping stoke nationalist, anti-Kurdish sentiment, which can only help at the polls.

For those concerned about the rise of ISIS -- including the United States, the Syrian people and countless other victims of the terrorist group -- the new turn of events is yet another bit of dispiriting news.

Whether the United States agreed to look the other way or was hoodwinked by Turkey, the losers are the Kurds, the many victims of ISIS and the prospects for victory against a shockingly ruthless and extremely dangerous organization.