For how long had the invasion of Libya been planned?

Miscellaneous Current Events
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From http://www.debka.com/article/20708/:

Hundreds of US, British and French military advisers have arrived in Cyrenaica, Libya’s eastern breakaway province, DEBKAfile’s military sources report exclusively. […] The advisers, including intelligence officers, were dropped from warships and missile boats at the coastal towns of Benghazi and Tobruk Thursday Feb. 24, for a threefold mission:

  1. To help the revolutionary committees controlling eastern Libyan establish government frameworks for supplying two million inhabitants with basic services and commodities;
  2. To organize them into paramilitary units, teach them how to use the weapons they captured from Libyan army facilities, help them restore law and order on the streets and train them to fight Muammar Qaddafi’s combat units coming to retake Cyrenaica.
  3. To prepare infrastructure for the intake of additional foreign troops. Egyptian units are among those under consideration.