In fact, it was mainly his zeal and enthusiasm to embark in the undertaking which was the means of deciding Gabinius to consent to Ptolemy's proposals.
The danger and difficulty which they considered as most to be apprehended in the whole expedition was the getting across the desert to Pelusium.

In fact, the great protection of Egypt had always been her isolation.

The trackless and desolate sands, being wholly destitute of water, and utterly void, could be traversed, even by a caravan of peaceful travelers, only with great difficulty and danger.

For an army to attempt to cross them, exposed, as the troops would necessarily be, to the assaults of enemies who might advance to meet them on the way, and sure of encountering a terrible opposition from fresh and vigorous bands when they should arrive--wayworn and exhausted by the physical hardships of the way--at the borders of the inhabited country, was a desperate undertaking.

Many instances occurred in ancient times in which vast bodies of troops, in attempting marches over the deserts by which Egypt was surrounded, were wholly destroyed by famine or thirst, or overwhelmed by storms of sand.
These difficulties and dangers, however, did not at all intimidate Mark Antony.