After the creation of the Kingdom of Serbs, Croats and Slovenes, created by the victors after WWI, the English and the French, or better said, the state that was imposed without consultation and against the will of the Croat people, the protected and privileged Serbs used three types or modes of serbization of Croatia.
The self-governing Serb Orthodox church treated all Eastern Orthodox believers in Croatia as Serbs, although they included citizens of various Balkan ethnic groups, and as such it forced them through Orthodox churches, by religious instruction in schools, army, police and state administration, whose chiefs were mostly Serbs.
Then followed the building of Eastern Orthodox churches all over Croatia, wherever there were military garrisons, police stations, for the religious conversion of Croats.
The colonization of Serbs in Croatia by method of agrarian reform, when they confiscated from the Croat people land and paid for it with useless certificates that they never paid for.
That was a legalized theft for settling Serbs, volunteers from WWI and Montenegrins.
Dr. Mladen Lorkovic in his work "People and Land of Croats" tried to establish and compare the volume of Serb colonization using the Yugoslav census from 1931. He says: "the increase in Serb population is not natural, but is the consequence of colonization of volunteers and colonists. 25 volunteer settlements were constructed near Osijek, and the same number near Vukovar. Between 20,000 and 25,000 persons were settled."
Dr. Milan Stojadinovic was one of the main factors of the Serb colonists in the Zagreb office for agrarian reform. The peasant rebellion in Kerestinec happened because of these colonists.
Due to settlement of Serb WWI volunteers in the Virovitica municipality the number of Croats fell from 80% in 1918 to 60%.
After the entry of Stjepan Radic into the Belgrade government, Pavle Radic and Gjuro Basaricek started to collect data about agrarian reform and colonization of Serbs on the account of Croats. They established that out of 50 colonies in Osijek and Vukovar regions, not a single one was a Croat colony. Then Pavle Radic and Gjuro Basaricek founded two Croat colonies. For full seven years the Serb press hadn't paid attention to the colonization but as soon as they found out about two Croat colonies, and in Croatia, Politika and other papers made a big deal, because Serbs were allegedly endangered. One newspaper suggested that those who work on the formation of Croat colonies should be killed. It should be mentioned that the assassin Punisa Racic, after killing Basaricek, told Stjepan Radic: "I've been looking for you!"
The situation was similar in Bosnia-Hercegovina. There 6,394 families were settled. If we take 5 persons per family on average, that means that more than 30,000 persons were settled.
The second plan for settlement in Croatia consisted of sending of frequently illiterate Serb clerks, who replaced professional staff from Croatia.
It is well known to what extent the Serb church was privileged. In 1921, the Serb Orthodox Church received state assistance from the budget amounting to 141,264,026 dinars, while the Catholic Church received 13,855,200 dinars.
Wherever there were Serb policemen, there an Eastern Orthodox church was built, at the best spot and on state expense.
Thus they built churches in Susak, Ston, on the island of Vis, in Maribor, Ljubljana, Celje etc. to let the foreigners who pass through see that Serbs are everywhere.
By the creation of the second Yugoslavia in 1945 Serbs gained total hegemony over the Croat people. The period between 1945 and 1990 has to be thoroughly investigated. Property of declared war criminals was looted and confiscated; in other words, the enemies of the people (which people?) were dispossessed in colonization, Serb colonies were set up along the Croatian Adriatic shore, [vacation] homes and spas were built in all larger towns for retired Serb military personnel. I will only mention Zagreb and Split.
In Split they built a whole settlement for 10,000 retired Serb officers, named Split 3.
They did the same in Zagreb. I've seen both with my own eyes. It will have to be established how many Serbs were settled and colonized in Croatia between 1918 and 1990 because in that period Coratia was occupied by Serbia.
Immigration and settlement of Serbs in that period is illegal. Those Serbs must leave the territory of the Republic of Croatia.
Russia occupied east and central Europe, where it stationed large military forces, which had to pull out from those countries after the liberation from the Russian occupation. These countries are Poland, Hungary, the former Czechoslovakia, Latvia, Estonia, and Lithuania. For Czechoslovakia, I know that it had 65,000 occupiers, while we should find out through Croat embassies the overall number of the mentioned occupation Russian forces.
The Republic of Croatia must demand that all Serbs settled between 1918 and 1990, during the occupation of Croatia, leave.
Serbs who were in mixed marriages and those who were born in Croatia and behaved correctly as citizens of Croatia, who did not bloody their hands, terrorize or maltreat Croats, can ask for permission to be given the Croatian citizenship.