To fall back upon

(Mil.) To retreat for safety to (a stronger position in the rear, as to a fort or a supporting body of troops).
To have recourse to (a reserved fund, a more reliable alternative, or some other available expedient or support).

See also: Fall, Fall

References in classic literature ?
She used to complain to me that she had nothing to fall back upon, that girls usually fall back upon; and I don't see how she is to have got over that since.
It was impossible to have given less encouragement than he had done to such a doctrine, but if we had not had the doctrine to fall back upon we should have deprived each other of some of our finest exhibitions.
His father had always ridden a good horse, kept a good house, and had the cheerful, confident air of a man who has plenty of property to fall back upon. Tom had never dreamed that his father would "fail"; that was a form of misfortune which he had always heard spoken of as a deep disgrace, and disgrace was an idea that he could not associate with any of his relations, least of all with his father.
Now, therefore, let us all do as I say; let us order the main body of our forces to fall back upon the ships, but let those of us who profess to be the flower of the army stand firm, and see whether we cannot hold Hector back at the point of our spears as soon as he comes near us; I conceive that he will then think better of it before he tries to charge into the press of the Danaans."
'That is quite possible,' remarked Heathcliff, forcing himself to seem calm: 'quite possible that your master should have nothing but common humanity and a sense of duty to fall back upon. But do you imagine that I shall leave Catherine to his DUTY and HUMANITY?
Earlier in the day I had arranged some likely articles on a side- table: my watch and chain, my bunch of keys, and two war-medals for plodding merit, and with a glance at these (as something to fall back upon), I stepped forward doggedly, looking
But there now followed an unfortunate interval of wet weather, during which she was obliged to fall back upon her sovereigns.
It had once or twice crossed his mind that possibly there was some deficiency in Dorothea to account for the moderation of his abandonment; but he was unable to discern the deficiency, or to figure to himself a woman who would have pleased him better; so that there was clearly no reason to fall back upon but the exaggerations of human tradition.
When President Muhammadu Buhari asked his ministers for comprehensive status reports on policies, programmes and projects on their ministries, departments and agencies on April 17, one of those who knew they have several publications to fall back upon was the minister of power, works and housing, Babatunde Raji Fashola (SAN).
"If there is no alternative left, the government will have to fall back upon the ordinance route," Joshi stated.
He advised them to arm themselves with lawyers and consultants, and to ensure they have the proper support structure to fall back upon in the event of backlash or complications.