This is a very rough translation since it goes Latin -> French -> English. I used Babelfish to help me figure out words in the French and correlated those to the Latin.
Whereas Louis the Great had reigned for 72 years, whereas the nations which betrayed the alliance were repressed and those which had been linked by the oath were reconciled during a four decade old war, peace was brought on ground and sea, in 1715.
As you can see, Latin is much more economical in its words…
Not exactly. Virtually any statement made in one language and translated into another is going to be longer in the second version.
English: As you can see, Latin is much more economical in its words.
Latin: Ut potes videre, Latina magis multo parsimonia est in verbis eis.
The Latin version of what you said is longer.
Also, I think the grammar in your version of the second line is a bit off: it looks to me like “with the nations repressed with agreements and [the nations] disorganized having been joined in war for four decades.”