Task: Explanation
Input (English): Raivis Zeltīts (born 21 March 1992 in Riga) is a Latvian politician, national-conservative activist, and writer. He is the Secretary General of the National Alliance, as well as board member and leader of its youth organization. He was elected to the Marupe municipal council in the 2013 municipal elections and re-elected in 2017. Has bachelor's degree in history. He is the author of many articles both in Latvian and English about nationalism, geopolitics, and the idea of Intermarium in today’s Europe. Liberal news magazine “New Eastern Europe” has called Raivis Zeltits “a key promoter of "identitaire" ideology in Latvian politics” and writes that with the national-conservative news portal “The New Nationalism” “Zeltīts has created a political platform, linking the far right from the Baltic to the Black Sea”. On the 23d of August 2017 Zeltīts' first book “Par Nacionālu Valsti” (“On Nation State”) was published. It describes the ideas and tasks of Latvian nationalism in the 21st century in a systematic way . Question: What was the planned, first devised by Raivis Zeltits, to form a federation of Central and Eastern European countries after World War I? Answer: Intermarium
Output (English):  He is the author of many articles both in Latvian and English about nationalism, geopolitics, and the idea of Intermarium in today’s Europe.