In his history of the Peloponnesian War, the ancient historian Thucydides spends much time describing ships: how many ships each side had, what the wind was like on the day of the battle, how the ships were fitted. Naval power and control of waters often constituted the difference between victory and defeat. The ancient Greeks built navies to protect their cities from pirates and defend sea trade routes, but they also emphasized naval power because Greece’s dispersed geography makes it highly vulnerable. Defending even smaller islands required ample ships, manpower and supplies.

Greece is not facing any invading force, but the challenge of geography remains the same. Even with the best equipment and resources — which cash-stripped Greece does not possess — it would be a difficult task for Greece to intercept every refugee boat entering its waters and ensure that all of its passengers remain, over a period of weeks and months, fully accounted for, registered, housed and fed.

Greece is a country of about 11 million people. Thus far this year, about 700,000 people crossed from Turkey to Greece. While many have already moved northward through Macedonia and Serbia into European Union countries, especially Germany, tighter regulations and new border controls have reduced this flow. Some countries have put up fences, making the journey to Austria and Germany more complex. Macedonia and other countries in the route northward have recently decided that they will only accept refugees from countries deemed unsafe, chiefly Syria, Iraq and Afghanistan. As a result, people arriving from countries like Iran and Pakistan are stranded in Greece.

Greece has been threatened, informally, with suspension from Schengen for its failure to secure its borders. Formally, on Dec. 2, European Immigration and Home Affairs Commissioner Dimitris Avramopoulos warned that Greece must improve the situation substantially at both land and sea borders by Dec. 17. The government in Athens is thus conflicted. On the one hand, Greece is in the midst of implementing its third round of bailouts and austerity measures. On Dec. 3, a general strike will likely take place in protest of changes to the pensions system. To address the ongoing refugee crisis, Greece needs more funding. Indeed, in August 2015, the European Union allocated over 470 million euros in emergency aid to Greece. On the other hand, the Greek government has been reluctant to accept more assistance from the Europeans. Greece has rejected the European offer to send officials to help at the Greek-Macedonian border and also failed to apply for extra assistance the country is entitled to under European Union regulations.

Greece’s hesitance can be explained by looking at its geography, the state of the European Union itself and the situation in Syria. As the despairing Greek migration minister said today, European Union governments “mistakenly believe that the refugee flow can be controlled from Greece.” Greece cannot fully control its borders without launching a vast naval blockade. Greece can, in theory, house the thousands of refugees who reach its borders, but the government in Athens knows that these refugees are not seeking a new life in a Greek state plagued by unemployment and seemingly never-ending austerity plans. These refugees will keep attempting to move north, and the Greeks do not wish to use coercive measures to stop them. At the same time, Greek decision-makers see that the European Union is divided, with many countries not willing to accept refugees relocated from Greece, or at least not willing to accept refugees in sufficient numbers. Greece thus fears that refugees who do not want to be in Greece will be stranded in the country, creating not only financial and logistical challenges, but significant tensions as well.

The Greek government is not fully cooperating with the European Union’s demands, in part because some of the demands regarding border policing are unrealistic, but also because non-cooperation could force the Europeans to accede to some of Greece’s demands and relocate more refugees. When governments across the European Union see a growing crisis in Greece, including lack of comprehensive registration of refugees, they are more likely to make concessions to Athens. Or at least that’s what the Greek sides hopes to achieve. Ultimately, the future of the refugee crisis hinges on developments in Syria.

As fighting continues raging, Greece will do its best to secure both financial assistance and firm guarantees that a significant number of refugees already in Greece or arriving in the country over the coming weeks will be relocated to other European countries. To achieve this goal, Greece — no stranger to discord and high-stakes negotiations with European institutions — will risk some of its privileges. Schengen is already eroding, with several countries already using ad-hoc border controls. Nevertheless, suspending Greece will do little to nothing to stem the tide of refugees. When it comes to Greece, the European Union is using Schengen as a negotiating tool. As Schengen’s future becomes more unclear and divisions within the European Union on how to address the refugee crisis grow, even this negotiating tool could erode quickly.