After Russia's military intervention in Syria in 2015 and the alleged interference in the 2016 election campaign in the U.S., relations between the Russian government and Obama administration became more strained. In September 2016, the U.S. government publicly accused Russia of "flagrant violations of international law" in Syria. Thomas Friedman opined, "Obama believed that a combination of pressure and engagement would moderate Putin's behavior. That is the right approach, in theory, but it's now clear that we have underestimated the pressure needed to produce effective engagement, and we're going to have to step it up. This is not just about the politics of Syria and Ukraine anymore. It's now also about America, Europe, basic civilized norms and the integrity of our democratic institutions." George Robertson, a former UK defense secretary and NATO secretary-general, said that Obama had "allowed Putin to jump back on the world stage and test the resolve of the West", adding that the legacy of this disaster would last.