The agreement “shall continue in force for a period of five years from the date it is made, and thereafter for successive five-year terms, unless and until terminated by one year prior notice in writing by either party.”

Because of the second comma, the phrase between the two comments can be ommitted if necessary. Had they written it like this: "shall continue in force for a period of five years from the date it is made, and thereafter for successive five-year terms unless and until terminated by one year prior notice in writing by either party.” then they would have to do the first five years before they could terminate the contract. Hope this helps.