The Maginot Line was built to fulfill several purposes:

• To avoid a surprise attack and to give alarm. 
• To cover the mobilization of the French Army (which took between 2 and 3 weeks). 
• To save manpower (France counted 39,000,000 inhabitants, Germany 70,000,000). 
• To protect Alsace and Lorraine (returned to France in 1918) and their industrial basin. 
• To be used as a basis for a counter-offensive. 
• To push the enemy to circumvent it while passing by Switzerland or Belgium.