Discover is a synonym of Observe. Observe is related to View. View is related to Corner. Corner is related to Road. 
Army can be used for Protection. Lock can be used for Protection. Lock can be used for Security. Security is related to Guard. 
Discover <--Synonym--> Observe <--RelatedTo--> View <--RelatedTo--> Corner <--RelatedTo--> Road 
Army --UsedFor--> Protection <--UsedFor-- Lock --UsedFor--> Security <--RelatedTo--> Guard 