Write SQL query to solve given problem: How many of the patients born in 1920s had pneumonia?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(DISTINCT T1.patient) FROM patients AS T1 INNER JOIN conditions AS T2 ON T1.patient = T2.PATIENT WHERE DESCRIPTION = 'Pneumonia' AND strftime('%Y', T1.birthdate) LIKE '192%'