Notice to employer
Primary source
Verbatim text below is from the Electronic Code of Federal Regulations (eCFR), a public-domain U.S. government work. Always verify the current version with the eCFR before relying on it for any legal matter.
Full Text
To be entitled to restoration rights under this part, an employee (or an appropriate officer of the uniformed service in which service is to be performed) must give the employer advance written or verbal notice of the service except that no notice is required if it is precluded by military necessity or, under all relevant circumstances, the giving of notice is otherwise impossible or unreasonable.
This is legal information, not legal advice. Laws vary by jurisdiction and change frequently. Always verify current law with official sources and consult a licensed attorney in your jurisdiction for advice on your specific situation.