Forcible self-help to protect nationals was discussed at length in the February issue of the "Naval War College Review," A practical example of this concept of international law can be found in the actions of the U.S. Navy in evacuating the nationals of 31 countries from the war zone during the 1956 Suez crisis.
Garrett, William B.
"The U.S. Navy's Role in the 1956 Suez Crisis,"
Naval War College Review: Vol. 23
, Article 11.
Available at: http://digital-commons.usnwc.edu/nwc-review/vol23/iss3/11