The second leg of the journey was almost entirely in pack ice (eliminating the submarine threat).

When do we expect the next submarine threat?

It seems that, in response to this new submarine threat, some alterations were made to Lusitania and her operation.

Once the navy became wary of the submarine threat, losses ceased.

The Australian authorities enjoyed only a brief break in the submarine threat.

The submarine threat was bad enough, but with the carrier group savaged the day before, the convoy was virtually naked to air attack.

The submarine threat is particularly strong in this scenario.

Over the ensuing three weeks, she screened the larger units of the fleet against a submarine threat that probably did not exist and sank mines.

It ruled out the submarine threat, and caused a refocusing on surface attacks.

As the submarine threat in the Gulf slowly abated, the air station concentrated on search and rescue activities.