HELLENIC STATE RAILWAYS: With the law 2144 of 18 March 1920 creates a public service under the name Sidirodromi Ellinikou Kratous (SEK) as a legal entity of public law, which undertakes the operation of the networks of the EES and SPAP. The SPAP in 1922 will secede and operate as an independent company. SEK will also take over the recently annexed lines Thessaloniki - Idomeni, Thessaloniki - Neos Kafkassos, Thessaloniki - Alexandroupolis, Sarakli - Stavros and Papapouli - Plati, which the Greek state will acquire by their legal, based on the original contracts, their owners. In 1932 the SEK absorbed the TSM and took over the line of Skidra - Aridea. Also during their operation the new connections Strimon - Promachon and Aminteo - Kozani were constructed. On 7 March 1954 it belongs to the SEK, due to exportationras from the Greek state, the line of JSC, Alexandroupolis - Ormenion. In 1955 the Thessaly Railway were nationalized and merged with the SEK. On 1 January 1971, the OSE was founded, which resulted from the transformation of the SEK, which ceased to exist permanently.