WASHINGTON -- Defense Secretary James N. Mattis shared the thinking behind the new National Defense Strategy during a discussion at the United States Institute of Peace in Washington on Tuesday.Released in January, the strategy sees Russia and China as the greatest threats, with Iran and North Korea as regional threats. Violent extremism rounds out the threat matrix.The strategy is based on a return to great power competition among the United States, Russia and China.POWER, URGENCY, WILLMattis told Stephen Hadley, the moderator of the event and former national security adviser to President George W. Bush, that in setting up the strategy, officials looked at threats from three different angles: power, urgency and will."In terms of raw power right now, I look at Russia and the nuclear arsenal they have," he said. "I look at their activities over the last 10 years from Georgia and Crimea to the Donetsk Basin to Syria and I can go on and on and on. In terms of just power, I think it is Russia that we have to look at and address."There are two threats that are most urgent right now: North Korea and the continuing fight against violent extremism. North Korea's nuclear and missile program -- in clear violation of United Nations sanctions -- remains a problem, and the current fight against violent extremists from the Islamic State to al-Qaida to Boko Haram to other transnational terror groups must be fought."In terms of will, clearly it is China," he said.China is different than Russia. "Russia wants security around its periphery by causing insecurity among other nations," he said. "They want a veto authority over the economic, the diplomatic and the security decisions of the nations around them."China seems to want some sort of tribute states around them," he continued. "We are looking for how do we work with China. I think 15 years from now we will be remembered most for how … we set the conditions for a positive relationship with China."COOPERATIONThe United States is looking for ways to cooperate with China, and that has been beneficial to both countries, Mattis said. He pointed to China's vote against the North Korean nuclear program in the United Nations Security Council as an example. He also pointed to the United States continuing freedom of navigation operations in international waters and airspace as an example of how the United States will confront China when it must."I have met with my counterpart in Beijing and in Singapore 10 days ago, and he will be here 10 days from now to continue that dialogue as we sort it out," Mattis said.Also part of the strategy are U.S. strengths, and foremost among them is the country's network of alliances and friends around the world. This network requires constant tending, the secretary said. He noted that just in the last month he has attended NATO meetings, consulted with Central and South American allies, and journeyed to Manama, Bahrain, to meet with Middle Eastern allies and friends.All of these were part and parcel of forming the National Defense Strategy.SOUTH ASIA STRATEGYThe secretary also spoke about the South Asia Strategy, announced in August 2017, and how that is proceeding. Officials continue to follow the strategy and it is making progress, but it is slow. It entails far more than just the military and far more than just the United States, he said.The strategy is a regional approach to the problem. It also reinforced the commitment to the area and realigned those reinforcements with Afghan forces. This was needed because the Afghans had an Army that wasn't ready to have the training wheels taken off the bike, Mattis said. "Only the Afghan special forces had mentors from NATO nations with them," he said. "And every time they went against the enemy, the Taliban, they won."But the rest of the Afghan forces were spread out around the country with no mentorship and no air support. The strategy changed that. The air support is crucial in giving Afghan forces the high ground in the mountainous country, "and that changes the tactical situation," the secretary said.Afghan forces are carrying the burden, with more than 1,000 dead and wounded in August and September, the secretary said, and they stayed in the field fighting. "And the Taliban has been prevented from doing what they said they were going to do, which was to take and hold district and provincial centers, [and] also disrupt an election that they were unable to disrupt," he said.But the most important aspect of the strategy is reconciliation. U.S. Ambassador Zalmay Khalilzad agreed to serve as a special envoy in Afghanistan specifically aimed at reconciliation between the Taliban and the government in Kabul. "He is hard at work on this, on an Afghan-led, Afghan-owned peace and reconciliation effort," Mattis said. "So this is the approach we're trying to sustain right now. It is working from our perspective, but what is heartbreakingly difficult to accept is the progress and violence can be going on at the same time."