ISIS caliphate in Iraq ‘has fallen’; Mattis says WH warning to Syria worked (for now); NATO’s plan to boost defense $pending; RoK’s Moon goes to Washington; And a bit more.

Iraq declares an end to the Islamic State’s caliphate. The announcement came this morning from the northern Iraqi city of Mosul, where an offensive has been ongoing for the last 255 days. "Their fictitious state has fallen," an Iraqi military spokesman, Brigadier General Yahya Rasool, told state TV.

Too soon? “Iraqi special forces reached the al-Nuri Mosque compound and took control of the surrounding streets on Thursday afternoon, following a dawn push into the area...where the IS militants are now making their last stand in what are expected to be the final days of the battle for Mosul,” Associated Press reports.

Adds Reuters: “The seizure of the 850-year-old Grand al-Nuri Mosque is a huge symbolic victory for the Iraqi forces fighting to recapture Mosul, which had served as Islamic State's de facto capital in Iraq.” However, “Iraqi authorities expect the long battle for Mosul to end in the coming days as the remaining Islamic State fighters are now bottled up in just a handful of neighborhoods of the Old City.”

So, what’s left? “The military estimated up to 350 militants were still in the Old City last week but many have been killed since. They are besieged in one sq km (0.4 square mile) making up less than 40 percent of the Old City and less than one percent of the total area of Mosul, the largest urban center over which they held sway in both Iraq and Syria,” Reuters, writes.

Grim scenes: “Damaged and destroyed houses dot the route Iraqi forces have carved into the congested district — along a landscape of destruction where the stench of rotting bodies rises from under the rubble,” AP reports. “There are hundreds of bodies under the rubble,” special forces Maj. Dhia Thamir told AP. That, here.

And in Syria, “Foreign fighters will die here. That’s the mission,” said the U.S. special envoy to the anti-ISIL coalition, Brett McGurk, of the ongoing operation to flush ISIS out of its de-facto HQs in Raqqa, Syria. McGurk sat down with Jenan Moussa‏ of Arabic Al Aan TV in Raqqa on Wednesday; and Moussa shared clips and transcripts of their chat, here. Read more on McGurk’s visit to Raqqa, via Reuters, here.

The U.S.-backed Syrian Democratic Forces fighting ISIS in Raqqa aim to impose a “complete siege” on the city, an SDF spox told Reuters this morning. He added that could take a couple days.

Apropos of nothing: Here’s video of U.S. Marines building a bridge in the vicinity of Raqqa, Syria.

Busy skies: U.S. Air Force RC-135s along with a U.S. Navy P-8 Poseidon aircraft have been flying in international airspace near Syria, The Aviationist reported after Monday’s warning from the White House to Damascus not to use chemical weapons again. Those aircraft happen to be “three of the most important ISR (Intelligence Surveillance Reconnaissance) assets in the U.S. inventory,” The Aviationist’s David Cenciotti writes. Read more on their capabilities, here.

By the way: Defense Secretary Jim Mattis said Wednesday that the Assad regime “took the warning seriously. They didn’t do it,” that is—carry out a chemical weapons attack between the warning Monday evening and events on Wednesday. Still lots of time, though.

Risk of Turkish-SDF clashes rises in Northern Syria. “Turkey has recently deployed reinforcements into the area, according to Turkey-backed rebel groups, prompting SDF concern that Ankara is planning to attack nearby areas that are under SDF control,” Reuters reports. “The Turkish military said on Wednesday it had fired artillery at YPG positions south of the town of Azaz in what it said was a response to the YPG's targeting of Turkey-backed rebels.” The SDF say the Turks fired first. More here.

From Defense One

It's Time for NATO to Look North // Julianne Smith and Rachel Rizzo: The alliance's six-year old maritime strategy quickly needs updating for the new (and more Russian) age.

Why Congress and the Pentagon Should Bypass Trump's Defense Spending Bill // Alex Wagner: The NDAA markup is a chance for leaders on Hill and the Pentagon to show they are the badly-needed adults in the room on defense spending.

Writing the Rules of Cyberwar // Alyza Sebenius: The line between offensive and defensive attacks is far from clear, a new book argues.

Welcome to Thursday’s edition of The D Brief by Ben Watson. Have something you want to share? Email us at the-d-brief@defenseone.com. (And if you’re reading this on our website, consider subscribing. It’s free.)

Overnight: The Senate and House Armed Services committees passed versions of the 2018 National Defense Authorization Act. The House panel approved the measure, which includes $696 billion for the Pentagon, shortly before midnight. Check out the Global Business Brief later this morning for more.

SecDef Mattis says the U.S. military will be forward-deployed to eastern Europe through 2020. Stars and Stripes: “Today, that commitment is embodied in the buildup of forces and increased U.S. spending to increase training and exercises with NATO and partner forces, he said. Some 1,000 U.S. soldiers from the 2nd Squadron, 2nd Stryker Cavalry Regiment, are leading a Poland-based battle group of an enhanced forward presence in Europe. Four multinational battle groups, totaling about 4,500 troops from 15 member nations, conduct exercises and train to quickly mobilize.”

Said Mattis on the “why” of extending the mission: “Russia must know what we stand for, and equally, what we will not tolerate. We stand for freedom and we will never surrender the freedom of our people or the values of our alliance that we hold dear.” Read the rest, here.

In NATO news, alliance members “plan to boost their defense spending by 4.3 percent this year, Secretary General Jens Stoltenberg said Wednesday, a response in part to intense pressure from President Trump that the nations invest more in their militaries,” the Washington Post reports from Brussels.

If you’re counting at home, “The spending increase announced Wednesday is $12 billion more than 2016 levels, and the increases are also growing bigger — 2016 spending was 3.3 percent higher than 2015 levels. Still, only five of NATO’s 29 members meet the spending guidelines. Romania plans to get there this year, while Lithuania and Latvia expect to meet the bar in 2018.” More here.

President Trump meets with new South Korean President Moon Jae-in today at the White House. The Wall Street Journal lays out the quick differences between the two world leaders: “Mr. Moon, South Korea’s first left-leaning president in nearly a decade, has called for closer ties with North Korea, primarily through economic cooperation, while the Trump administration has called for tougher sanctions, military pressure and diplomatic isolation.” Read the Journal’s preview, here.

Trump’s National Security Adviser, Lt. Gen. H.R. McMaster, said Wednesday “Moon's visit would include discussions on a new approach to North Korea,” CNN reported. "The reliance on China to pressure North Korea diplomatically continues but if Pyongyang conducts another underground test, the US may decide that the strategy is not working. 'All options' are on the table if a test happens, one military official emphasized, while underscoring the hope that diplomatic pressure works." More here.

Staying in the region, the U.S. and Australia began “their biggest ever joint military exercises on Thursday, a show of force, largely at sea, aimed at sending a message both to allies and potential foes, including China,” Reuters reports this morning from Sydney. “The exercises involving 33,000 U.S. and Australian troops on board battleships equipped with strike jets, comes as tension over China's more assertive activity, particularly in the disputed South China Sea, has raised fears of confrontation.” Short story, here.

At the intersection of new technology and war, we have the Philippines special operations forces, who are integrating drone footage to print updated maps of the city of Marawi. VICE News visited the scene and embedded with Philippin SOF to file this nearly 10-minute video report.

New this morning: Reuters has an exclusive report claiming President Duterte’s drug war has “delivered hundreds of drug suspects to Manila hospitals. A Reuters investigation has revealed almost all were dead on arrival. Witnesses and family members say they were executed and their bodies removed from the scene in a police cover up.” That #LongRead, here.

Lastly today: The wages of war—Cholera hits South Sudan. “The fast-developing, highly contagious infection can spread in areas without clean drinking water and with poor sanitation. It can result in death through dehydration if left untreated,” AP reports Pieri, South Sudan. The country has already topped more than 11,000 cases of Cholera, “including at least 190 deaths...which coincides with the recent surge of displaced people across the country as civil war moves well into its fourth year.”

About the city of Pieri: “Due to fighting between South Sudan’s government and opposition forces in surrounding areas, Pieri’s population has tripled since February. Once a town of roughly 15,000 inhabitants, it now hosts an additional 30,000 displaced people.” Add to that, “Central Pieri has only two wells serving 5,000 people. Those unable to reach the wells have started drawing water from the filthy swamps.”

Adds AP, in closing: “The mass displacement of people, like the civil war itself, shows no signs of slowing.” Story here.

Not to be forgotten: Cholera continues to slam Yemen, too—with 208,203 cases reported, and 1,344 deaths; Houthi-controlled regions are among the hardest hit. View a map of the ongoing damage, here.