After months of deliberations, Turkey began to take delivery of the Russian S-400 missile defense system last week. The first batch of equipment arrived two days before the third anniversary of the 2016 coup attempt. In the coming days, experts will discuss the S-400 delivery's impact and the significance of the July 15, 2016, coup attempt together. We will observe how politicians respond to the arrival of a weapon vital to Turkey's national security. Let us see whether opposition leaders will side with the Turkish government, maintaining that national security is a shared goal and that it is time for solidarity – or speak Washington's language to point fingers. The opposition's response to the S-400 delivery will make a permanent impact on Turkish politics. An overwhelming majority of the Turkish people see the Russian system as a matter of national security and therefore above party politics. To be clear, the S-400 system strengthens Turkey's hand in the brewing fight over energy reserves in the Eastern Mediterranean. Against the backdrop of heightened national fervor on the coup attempt's anniversary, let us hope that everyone will respond to this significant development in the spirit of unity. NATO was first to respond to the S-400 delivery. Concerned about the "potential results" of this development, it stressed the importance of interoperability among member states. It remains unclear whether NATO members will have problems working together with Turkey in the future. After all, Washington's reaction, rather than NATO's response, remains the key question. An excessive response would not just jeopardize the future of Turkey-U.S. relations but weaken the alliance if tensions between two major allies spin out of control. The U.S. had been threatening to remove Turkey from the F-35 fighter jet program and impose Countering America's Adversaries Through Sanctions Act (CAATSA) sanctions on its NATO ally. To be clear, President Donald Trump disagrees with the Congress, the Pentagon and the State Department on this issue. The U.S. president blames the current dispute on the Obama administration's failure to sell the Patriot missile defense system to Turkey. He concedes that the Turks were right to take this step. Yet the Pentagon desperately wants to remove Turkey from the F-35 program, which has nothing to do with CAATSA. U.S. officials make the case that the S-400s would jeopardize the safety of F-35s, and clearly, do not want the Turks to have both the S-400 and the F-35s to challenge the military balance of power in the region. As for sanctions, President Recep Tayyip Erdoğan has urged President Trump to grant a waiver. Trump's response will become clear in the coming days. A complete waiver, a 180-day delay, mild sanctions and harsh sanctions are all on the table. Since Turkey has already taken delivery of the S-400 system, the ball is now in Washington's court. In other words, the skills of U.S. policymakers working on Turkey policy will be put to test. Their strategic choices and visions will manifest themselves soon. The Turkish government, in turn, has explained the S-400 system's significance to the domestic audience in great detail. The relevant agencies have completed their preparations. It is time to resist Washington's pressure together. The government and the opposition must leave aside their political differences and work together to ensure our nation's safety. The July 15 resistance's inclusiveness offers a useful starting point. Let us seize it. [Daily Sabah, 15 July 2019]