The European Union's unity, solidarity, and international reputation are in jeopardy due to various issues including Greece's debt, Russia's involvement in Ukraine, Britain's efforts to alter its relationship with the bloc, and Mediterranean migration. Failing to effectively address any of these challenges would exacerbate the others, increasing the dangers faced by the EU as a whole. The immediate threat is Greece's potential default and the possibility of it leaving the euro currency, known as 'Grexit', which undermines the concept of a closer union among European countries. According to Fabian Zuleeg and Janis Emmanouilidis of the European Policy Centre, the long-term repercussions of Grexit would have a significant impact on the European project, setting a precedent and further weakening the EU's fundamental purpose. Despite Greece's small size in terms of economic output and population within the euro zone and EU, its state bankruptcy following two large bailouts totaling nearly 200 billion euros ($220 billion) has dealt a significant blow to EU prestige. Before the results of Sunday's Greek referendum were revealed, tensions were high in Brussels with Greeks blaming Germans, others blaming Greeks, Keynesian economists criticizing austerity measures, and EU officials highlighting the success of bailouts in other parts of the bloc. While the future of Greece remains uncertain, it has already demonstrated that the belief in the unbreakable nature of Eurozone membership was misguided. Efforts may now be made by Greece's partners to strengthen the remaining members of the euro zone and address some of the initial flaws in the monetary union, although opposition from Germany may hinder progress towards joint government bond issuance. The Greek situation will serve as a lesson for markets in the event of future economic downturns or spikes in sovereign bond yields within the euro zone. Destabilizing Greece's economy could have serious consequences, including causing suffering and financial losses for European taxpayers. This collapse could also worsen Europe's existing crises and unsettle the fragile southern Balkans. Given the already high tensions in the eastern Mediterranean due to various conflicts and disputes, a weakened Greece may seek assistance from Russia. This could potentially lead to Greece blocking EU sanctions against Moscow or offering naval facilities to Russia. Additionally, Greece is struggling with an influx of refugees from conflicts in Syria and Iraq, who are seeking passage to wealthier European countries like Germany and Sweden. The cash-strapped Greek government is eager to see these refugees move on to other EU countries for asylum. Imagining a scenario where a government expelled from the euro zone uses migrants to pressure EU countries is not difficult. The crisis involving "boat people" has caused division within the EU, with Italy and other frontline states criticizing their northern and eastern counterparts for not showing solidarity by refusing to share the burden of refugees. Britain has also declined to accept any refugees. The failure to resolve Greece's debt crisis after five years has made the EU appear weak and divided to leaders such as Russian President Vladimir Putin and Chinese President Xi Jinping, who are eager to expand their influence. Brussels officials admit that the euro zone crisis has led to a resurgence of national decision-making on certain policies and weakened Europe's model of supranational governance based on rules. The EU's position in global trade and climate change talks has been compromised due to Britain's push to renegotiate its EU membership terms and hold a referendum by 2017. This raises concerns about the EU potentially losing its second largest economy, main financial center, and joint strongest military power. Despite polls showing majority support for remaining in the EU, there is anxiety in Brussels following the unexpected outcome of the May general election in the UK. Following his win, Cameron has faced opposition from Eurosceptic members of his own party. If Greece faces a prolonged economic crisis, this could support the argument that the UK is too closely tied to a failing system. Russia, who still harbors animosity towards the UK, would likely be pleased if they were to leave the EU, as it would weaken EU members who are standing up to Russian aggression in Ukraine and Georgia. Despite this potential shift, the UK would remain part of NATO, which could give Putin more leverage in negotiations with Chancellor Merkel of Germany. Rem Korteweg from the Centre for European Reform draws a comparison between the current interlocking crises and the four horsemen of the apocalypse in the New Testament Book of Revelation. He sees them as symbols of conquest, war, famine, and death, representing a "day of judgment." Korteweg believes that EU leaders will struggle to control these crises and prevent chaos, instability, and blame within the EU if a unified European response is not developed.