MILITARY veterans have long been accustomed to a relatively easy mortgage process. Even borrowers with no down payment or a low credit score were usually granted V.A. loans, in large part because the Department of Veterans Affairs insures a quarter of the loan amount.

But about two years ago, lenders began limiting the conditions under which they would offer these mortgages, and industry executives say that since the start of the year, all the nation’s major lenders have followed suit.

“It’s been a tightening across the board,” said Nathan Long, the chief executive of VAMortgageCenter.com, an online broker of V.A. mortgages.

Lenders will still offer V.A. loans with no down payment, he said, but “if you have a credit score of 610, the best thing to do is work on your credit and try again in a couple of months, because you don’t really have any options.”