Trump is on opposite sides of so many issues, changing his stance and tone with little (usually no) public reason, that his own advisers are regularly contradicting his stances, seemingly with no care for what the president has previously said. This is bad for efficient policymaking domestically, and it is dangerous for foreign policy. Other countries are less able to understand what's going on below the surface in Washington, and more likely to misinterpret the administration's intentions, increasing the chances of war around the world.
Another possibility, especially on the international stage, is that mixed signals could stir confusion and even strife. Trump has taken a belligerent stance with China, calling on it to do more to curb North Korea’s nuclear program, saying that the longstanding One China policy is negotiable, threatening a trade war, and warning about its building islands on the South China Sea—all of which has caused Chinese state media to raise the specter of war. Tillerson has echoed some of Trump’s hawkishness on China, but in modulated ways, and on the issue of North Korea he takes a very different line: that the United States has to be “clear-eyed” in what can realistically be expected from the Chinese government. If relations between China and the U.S. deteriorate, as seems likely, there will be the added problem of who the Chinese government tries to engage with in their negotiations. Will they think the relatively conciliatory Tillerson is setting policy, in which case changing policy on North Korea can be regarded as secondary? Or will they believe Trump is driving policy, in which case they will go into negotiations with greater pessimism about finding common ground?
If the Chinese government listens to Tillerson, it’ll be clear that the word of the American president carries little weight. If they listen to Trump, they’ll conclude that their relationship with the U.S. can’t be fixed. Both outcomes are troubling.
U.S. policy toward Russia has the greatest potential for disaster. Given the growing anti-Russia sentiment on Capitol Hill and the Pentagon, strengthened by reports of Russian interference in the election, Mattis might feel more beholden to hawks in Congress than the president he’ll serve under. In fact, Mattis might feel the need to take a firmer line against Russia to compensate for Trump’s gestures of friendship to Vladimir Putin.
The danger is that Putin will see Trump’s victory as an irresistible window of opportunity to test the fragility of NATO, only to encounter Mattis-led resistance. If so, conflict with Russia becomes more likely, not less.
Back in 1950, the U.S. sent mixed messages about its relationship with South Korea. Formally, the Truman administration was committed to a policy of containment of communism, but in speech that year, Secretary of State Dean Acheson failed to mention the country in describing the U.S.’s “defensive perimeter” in Asia. Dispatches between the U.S. and its embassy in Moscow, which were intercepted by the Soviets, also suggested that South Korea was a low priority. As a result, Soviet dictator Joseph Stalin made the made miscalculation that he could greenlight a North Korean invasion of South Korea, with little risk of American resistance. So began the Korean War.