"We will never forget the images of planes vanishing into buildings; of billowing smoke rolling down the streets of Manhattan; of photos hung by the families of the missing," he wrote. "We will never forget the rage and aching sadness we felt. And we will never forget the feeling that we had lost something else: a sense of safety as we went about our daily lives."
He went on to write that his "greatest responsibility is the security of the American people."
"It is the first thing I think about when I wake up in the morning," wrote the president. "It's the last thing I think about when I go to sleep at night. That responsibility is the heart of the policies my administration has put in place."
The president goes on to detail his efforts to keep America safe, which include increasing the size of the Army and Marine Corps.
"No one can guarantee that there will never be another attack; but what I can guarantee - what I can promise - is that we will do everything within our power to reduce the likelihood of an attack, and that I will not hesitate to do what it takes to defend America," he writes.