If you get really stuck, you may find these passwords helpful. All passwords give the maximum score possible up to that point

Mission 1	Baptism Of Fire	No need - first mission
Mission 2	A Quiet Blow-Up	YJJXB
Mission 3	Reverse Engineering	4FQBF
Mission 4	Restore Pride	5DNCQ
Mission 5	Blind Justice	6S5TL
Mission 6	Menace Of The Leapold	AT1WN
Mission 7	Chase Of The Wolves	O9VJ8
Mission 8	Pyrotechnics	WQ9XB
Mission 9	A Courtesy Call	Q2AXT
Mission 10	Operation Icarus	TUGPD
Mission 11	In The Soup	9WODW
Mission 12	Up On The Roof	UVHDC
Mission 13	David And Goliath	FBK48
Mission 14	D-Day Kick-Off	WA8DW
Mission 15	The End Of The Butcher	KEWD3
Mission 16	Stop Wildfire	 R7IP3
Mission 17	Before Dawn	FXIMV
Mission 18	The Force Of Circumstance	ZZMJV
Mission 19	Frustrate Retaliation	8HCWN
Mission 20	Operation Valhalla	C7KWW