It wouldn't make sense to add new weapons. How many weapons were developed between yesterday and today, how many entered service in the army between yesterday and today? Exactly.
That's the amount of time between HL2 and the episodes. Each picks up where the other ends.
--------------------------------------------------------------------------- In the end they will lay their freedom at our feet and say to us, 'Make us your slaves, but feed us.'
--------------------------------------------------------------------------- In the end they will lay their freedom at our feet and say to us, 'Make us your slaves, but feed us.'