Adams (plaintiff) secured a patent for a non-rechargeable electrical battery comprised of magnesium and cuprous chloride electrodes, which used water as battery fluid. After filing for the patent, Adams presented his invention to the United States Government (defendant). Although the Government originally determined that the battery was unworkable, it subsequently changed its position and ultimately began using the battery without notifying Adams. Adams filed a patent infringement suit against the Government. The Government contended that the patent was invalid for obviousness under 35 U.S.C. § 103. In support of its argument, the Government presented various patents and treatises describing zinc and silver chloride batteries, and contemplating the use of a magnesium electrode but intimating that such use would not be successful. The Government contended that these prior references taught the substitution of a magnesium electrode for zinc, as Adams did in his patented battery. In addition, the Government offered prior art patents purportedly teaching the substitution of a cuprous chloride electrode for a silver chloride one. Although none of the references specifically suggested that a water-activated battery using magnesium would be successful, the Government contended that Adams’ battery was not patentable because wet batteries utilizing zinc and silver chloride were known in the art at the time of filing, and additional prior art established that magnesium and cuprous chloride could be substituted for zinc and silver chloride. The Trial Commissioner held the patent valid and infringed. The Court of Claims affirmed. The Supreme Court granted certiorari.