What you have descirbed is not correct. The details differ with different products but, if you have the numbers correct it probably means that you need something like this
Servo.writeMicroseconds(700);
delay(100);
Servo.writeMicroseconds(2000);
What you are trying to do is mimic the process of the user pulling the joystick all the way back and then pushing it all the way forward. I suspect that should be followed by another
Servo.writeMicroseconds(700);
so that it does not start at full speed.
The details will be in the ESC user manual.
...R