Simplify the following text for a Grade 9 native English-speaking person.
Original: While the strategy of pushing the Viá '' t Minh into attacking a well defended base in a remote part of the country at the end of their logistical trail was validated at the Battle of Na San , the lack of construction materials ( especially concrete ) , tanks ( because of lack of road access and difficulty in the jungle terrain ) , and air cover precluded an effective defense .
Simplified: The French had the stategy of pushing Viá '' t Minh into attacking a well defended base in a remote part of the country at the end of the logistical trail . This strategy was validated at the Battle of Na San .