Always be aware of your enemies vision range, never assuming that they cannot see you. There is a good chance that the soldier will move around and will spot you. Use the "Eye" tool and place it on an enemy soldier to reveal his vision range. Keep in mind, if your commando is standing up and is in the "light" area of the vision range, he will be seen but it will take about five to ten seconds for your enemy to react. During this time, go into crawl mode. If you are in crawl mode and are in the "light" area of the soldier's vision range, you will not be seen. However, if you are not using the spy and are wearing an enemy uniform, you will not be seen even when standing. However, the darker area of the vision range is the hot zone. You will be seen, and the enemy will automatically react no matter what, except if you are using the spy.