Complex sentence: A force of 1,700 Marines occupied an area containing a number of foreign embassies, the locale was proclaimed an International Security Zone by the Organization of American States earlier in the day, OAS also issued a resolution calling the combatants to end all hostilities.
Split into simpler sentences: A force of 1,700 Marines occupied an area containing a number of foreign embassies, the locale was proclaimed an International Security Zone by the Organization of American States (OAS). Earlier in the day, OAS also issued a resolution calling the combatants to end all hostilities.