As a subject matter expert in military protocol and customs, I can provide you with a detailed explanation regarding the tradition and rules of saluting within the military, particularly in relation to the Secretary of Defense.
Military customs and courtesies are an integral part of military life, and the salute is one of the most visible and recognized of these customs. It is a sign of respect and acknowledgment of authority. The act of saluting is governed by a set of rules that dictate when and to whom it is appropriate to render this gesture.
Saluting the Secretary of Defense:
The Secretary of Defense is a civilian official appointed by the President of the United States and confirmed by the Senate. They are the head of the Department of Defense and have oversight over all branches of the military. As such, the Secretary of Defense holds a position of high authority and respect within the military hierarchy.
According to military protocol, it is customary for service members to salute the Secretary of Defense as they would any other senior official who holds a position of authority. This includes the President, Vice President, Service Secretaries, and all superior commissioned and warrant officers. The salute is a way of showing respect for the office they hold and the responsibilities they carry.
When to Salute:
The decision to salute is not solely based on the rank or position of the individual but also on the context and setting. Here are some general guidelines:

1. Outdoors: Saluting is typically done outdoors. When you encounter the Secretary of Defense or any superior officer outdoors, rendering a salute is expected.

2. Indoors: The rules for saluting indoors are more nuanced. Traditionally, saluting indoors is not required, except in certain circumstances such as when reporting to an officer or when in the presence of the President, Vice President, or the Secretary of Defense. The rationale behind this is to avoid constant saluting in confined spaces where military personnel may frequently pass by each other.

3. Dress Uniforms: When in uniform, particularly dress uniforms, it is more likely that you will be expected to salute. In casual or utility uniforms, the expectation may be less formal.

4. Medal of Honor Recipients: It is also a military custom to salute all recipients of the Medal of Honor, regardless of their rank or whether they are in uniform.

5. Foreign Officers: When interacting with superior officers of friendly foreign nations, rendering a salute is a sign of international courtesy and respect.
How to Salute:
The proper way to salute is with a prompt removal of the headgear with the right hand, if not in uniform, or with a sharp, precise motion of the right hand to the forehead if in uniform. The hand should be flat with the fingers together, and the palm should face downward slightly. The salute should be held for a moment and then smartly dropped.
Conclusion:
In conclusion, whether or not you have to salute the Secretary of Defense depends on the circumstances. It is a gesture of respect and acknowledgment of the high office they hold. Understanding the context and setting, as well as the specific rules of military protocol, is crucial to ensuring that this custom is observed correctly and with the appropriate level of respect.
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Saluting. ... You salute the President, Vice President, Secretary of Defense, Service Secretaries, all superior commissioned and warrant officers, all Medal of Honor recipients, and superior officers of friendly foreign nations. 1.6.1.2. You do not, typically, salute indoors.Aug 7, 2012read more >>