Is it true that some medical schools reserve a portion of their new admissions for people who commit to military duty?

my friend told me her son is trying to get into Johns Hopkins Medical School. She said that they reserve a certain amount of new admissions to people who commit to the military or who are in the military. I guess that’s so the military has a guaranteed amount of doctors that are committed to serve. I have never heard this before. I know medical schools are very competitive and usually take the top kids from the top schools. Not that her son did not do well, but he’s not from a top school.

Does anybody know if this is true? Do some or all medical schools reserve a certain amount of new admissions for people who will become doctors and serve in the military?