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KNOW IT ALL: Thursday's Top 6 Stories at NBC News

From anti-ISIS forces stepping up attacks in Iraq to historic talks in Cuba with the U.S., see the stories we're following.

Good morning. Here are some of the stories we’re following today:

1. Anti-ISIS forces secretly battling militants in Mosul

The ISIS stronghold of Mosul — Iraq's second-largest city — has been under intense fighting with hundreds of guerrilla attacks against the Islamist militants who now control it, Iraq's vice president told NBC News. Carrying out those attacks are volunteers with the "Mosul Liberation Battalions" — the little-known resistance movement that has killed "a large number" of extremists through operations, according to Vice President Osama al-Nujaifi. Battalion members include former military officers and tribesmen as well as students and local businessmen. But they're largely going it alone. "The government cannot send them anything," al-Nujaifi said. "All their operations are planned and implemented according to resources they have." Read more in NEWS.

2. Historic talks begin to open trade between U.S.-Cuba

A U.S. delegation arrived in Havana on Wednesday for the first time in nearly 40 years to talk about re-establishing diplomatic ties between the estranged countries. And for Cuban-Americans, the move is highly anticipated. "I view it as a sign of progress in the relationship between us and Cuba," one Florida resident told NBC News. "I don't think the embargo has worked and the idea of doing something repeatedly is insane." The high-level talks through Friday would set the stage in the next few months for a trip by Secretary of State John Kerry, and eventually, lifting trade restrictions, U.S. officials say. Read more in LATINO.

3. Measles outbreak prompts reconsidering booster shots

A measles outbreak has grown to 59 confirmed cases in California, including workers at Disneyland, as well as other states. Now, health officials are encouraging those who've been vaccinated to take extra precaution. Many adults who were vaccinated for measles decades ago as children are now highly susceptible to the virus. That's because as the years pass, people lose their original protections from childhood vaccines that come in the form of disease-battling antibodies and "memory cells" that attack infections if the body is ever exposed again, doctors say. Read more in HEALTH.

4. Alleged ‘Capitol Bomber’ indicted for attempted murder

The 20-year-old Ohio man arrested last week and accused of plotting to bomb the U.S. Capitol was indicted by a federal grand jury Wednesday, including for allegedly attempting to murder government officials. Christopher Lee Cornell is scheduled to appear in federal court Thursday afternoon. In addition to the attempted murder count, the indictment charges Cornell with solicitation to commit a crime of violence and possession of a firearm in connection with a crime of violence. His father told NBC News that Cornell had converted to Islam, but wouldn't have actually carried out the alleged terror plot. Read more in NEWS.

5. Why deflating a football before a game is difficult

As the New England Patriots await an NFL investigation into how 11 of 12 footballs used during the AFC championship game Sunday came to be under-inflated, one former ball boy told NBC News that it can be very difficult to tamper with the pigskins. After balls were inspected, according to former Chicago Bears ball boy Eric Kester, the game balls were taken right out to the field. "There was a window, maybe an hour or so, between inspection and game time," he said. "The balls were out on the field, and it would have been very difficult for me to secretly deflate balls while thousands of fans and media members moved about the stadium." Read more in INVESTIGATIONS.

6. Sex assault claims against Cosby are ‘painful,’ TV son says

Actor Malcolm-Jamal Warner, who played Bill Cosby's fictional son, Theo Huxtable, said it has been "painful" to watch the comedian deal with sexual assault allegations made against him. In an interview with Billboard, Warner said his "Cosby" co-star has been a big influence in his life. "Just as it's painful to hear any woman talk about sexual assault, whether true or not, it's just as painful to watch my friend and mentor go through this," Warner said. Cosby through his lawyers has denied the assault allegations, which have resurfaced in recent months but span past decades. Read more in POP CULTURE.

… What’s trending today?

During the Australian Open on Wednesday, the tennis world’s no. 7-ranked woman, Eugenie Bouchard of Canada, was asked to give a “twirl, like a pirouette” by a male interviewer. In front of spectators, the 20-year-old awkwardly complied.

Some on social media say the request came off sexist, but Bouchard had her own comeback: "I don't know, an old guy asking you to twirl. It was funny."