This is a list of the world's largest armies, measured by the number of soldiers in uniform. This is not a list of the world's strongest armies, since military power is not simply a function of headcount.
Protocol is defined as the rules and customs of a group or a standard procedure. An example of protocol is the method by which a learning center must document their students' progress. YourDictionary definition and usage example.
Email Protocols: IMAP, POP3, SMTP and HTTP. Basicaly, a protocol is about a standard method used at each end of a communication channel, in order to properly transmit information. In order to deal with your email you must use a mail client to access a mail server.