"The hand of the aggressor is stayed by strength – and strength alone."
Simple: What keeps the enemy together is his strength - and only his strength.
"We must be ready to dare all for our country. For history does not long entrust the care of freedom to the weak or the timid. We must acquire proficiency in defense and display stamina in purpose."
Simple: We must be brave and ready to give up everything for our county. This is because history does not allow people to take care of freedom if they are weak or afraid to do what needs to be done. We must be strong with our army and strong in our reason to fight.