The Holocaust: Almost all Jews in Bulgarian-occupied Western Thrace were deported to Treblinka extermination camp to be killed.

The Holocaust, known in Hebrew as the Shoah, was the genocide of European Jews during World War II. From 1941 to 1945, Nazi Germany and its collaborators systematically murdered some six million Jews across German-occupied Europe, around two-thirds of Europe's Jewish population. The murders were committed primarily through mass shootings across Eastern Europe and poison gas chambers in extermination camps, chiefly Auschwitz-Birkenau, Treblinka, Belzec, Sobibor, and Chełmno in occupied Poland. Separate Nazi persecutions killed millions of other non-Jewish civilians and prisoners of war (POWs); the term Holocaust is sometimes used to include the murder and persecution of non-Jewish groups.

In March 1943, about 4,075 Jews living in Bulgarian-occupied eastern Greek Macedonia and Western Thrace were deported to Treblinka extermination camp and murdered. In an operation coordinated by Bulgaria and Germany, almost all Jews in Bulgarian-occupied Greece were rounded up on the early morning of 4 March 1943, held in camps in Bulgaria, and reached Treblinka by the end of the month. The death rate of 97 percent of the Jews living in the area in 1943 was one of the highest in Europe.

Treblinka was the second-deadliest extermination camp to be built and operated by Nazi Germany in occupied Poland during World War II. It was in a forest north-east of Warsaw, four kilometres south of the village of Treblinka in what is now the Masovian Voivodeship. The camp operated between 23 July 1942 and 19 October 1943 as part of Operation Reinhard, the deadliest phase of the Final Solution. During this time, it is estimated that between 700,000 and 900,000 Jews were murdered in its gas chambers, along with 2,000 Romani people. More Jews were murdered at Treblinka than at any other Nazi extermination camp apart from Auschwitz-Birkenau.