Apart from the property issue, there were many other parts of the plan that sparked controversy. For example, the agreement envisaged the gradual reduction in the number of Greek and Turkish troops on the island. After six years, the number of soldiers from each country would be limited to 6,000. This would fall to 600 after 19 years. Thereafter, the aim would be to try to achieve full demilitarisation, a process that many hoped would be made possible by Turkish accession to the European Union. The agreement also kept in place the Treaty of Guarantee – an integral part of the 1960 constitution that gave Britain, Greece and Turkey a right to intervene militarily in the island's affairs. Many Greek Cypriots were concerned that the continuation of the right of intervention would give Turkey too large a say in the future of the island. However, most Turkish Cypriots felt that a continued Turkish military presence was necessary to ensure their security. Another element of the plan the Greek Cypriots objected to was that it allowed many Turkish citizens who had been brought to the island to remain. (The exact number of these Turkish 'settlers' is highly disputed. Some argue that the figure is as high as 150,000 or as low as 40,000. They are seen as settlers illegally brought to the island in contravention of international law. However, while many accepted Greek Cypriot concerns on this matter, there was a widespread feeling that it would be unrealistic – and legally and morally problematic – to forcibly remove every one of these settlers, especially as many of them had been born and raised on the island.)