US Senator Ben Sasse, a member of the Senate Armed Services Committee, issued a statement on Thursday following Defense Secretary James Mattis' resignation from his position. "This is a sad day for America because Secretary Mattis was giving advice the President needs to hear. Mattis rightly believes that Russia and China are clear adversaries and that we are at war with jihadists across the globe who plot to kill Americans at home. Isolationism is a weak strategy that will harm Americans and America’s allies. Radical Islamic jihadists are still at war with us, and no ISIS is not gone."