ISR is short for Intelligence, Surveillance, and Reconnaissance.
SSE stands for Sensitive Site Exploitation.
RTB is short for Return to Base.
A fragmentary order (or "Frag-O") is "an abbreviated form of an operation order, usually issued on a day-to-day basis that eliminates the need for restating information contained in a basic operations order. It may be issued in sections."Fragmentary orders are often necessary due to enemy action. Remember "no plan survives contact with the enemy." Expect fragmentary orders in most operations.They can only be issued if a complete combat order (known as a base order) has been previously issued. Fragmentary orders should cover only the information that has changed since the issuance of the base order. Frequently, the information changed pertains to enemy situation, mission,and execution of the plan. Fragmentary orders are an important technique to keep orders short. (In order to alleviate any potential confusion, if there are no changes to a particular paragraph, subparagraph, or section, the order issuer shall state the name of the section and "No Changes").
Charlie Mike is short for Continue Mission.