When Germany declared war, France implemented "Plan XVII" with five attacks, later named the Battle of the Frontiers. The German deployment plan, II, concentrated German forces (less 20 per cent to defend Prussia and the German coast) on the German–Belgian border. The German force was to advance into Belgium, to force a decisive battle with the French army, north of the fortifications on the Franco-German border. "Plan XVII" was an offensive into Alsace-Lorraine and southern Belgium. The French attack into Alsace-Lorraine resulted in worse losses than anticipated, because artillery–infantry co-operation that French military theory required, despite its embrace of the "spirit of the offensive", proved to be inadequate. The attacks of the French forces in southern Belgium and Luxembourg were conducted with negligible reconnaissance or artillery support and were bloodily repulsed, without preventing the westward manoeuvre of the northern German armies.