Germany under the Nazis began institutionalizing and segregating disabled people early in 1933 , but the major step toward systematic confinement and murder came in 1939 , with the start of the T4 “euthanasia” program targeting institutionalized disabled people.

What happened first

  • 1933: The Nazi state introduced policies that pushed disabled people out of normal civic life, including forced sterilization laws and growing pressure to keep them out of schools, work, and marriage.
  • 1934 onward: The sterilization system became operational, and institutions became one of the few places disabled people could remain in public life at all.
  • 1939: The regime began the organized killing of disabled children and adults, especially those already in institutions, through Aktion T4.

Why this matters

“Institutionalizing” can mean two different things here:

  1. Placing disabled people into segregated institutions , which intensified after 1933.
  1. Using those institutions as sites of mass murder , which began in 1939 with T4.

Concise answer

If you mean when Nazi Germany started systematically pushing disabled people into institutions and out of society , the answer is 1933. If you mean when it started using institutions as part of a killing program , the answer is 1939.

TL;DR: early exclusion and segregation began in 1933 ; organized murder in institutions began in 1939.