|Initial French advance, March 1799|
French advance into Liechtenstein on 6 March, 1799.
The map is an excerpt taken from the 2nd Military Survey of the Austrian Hungarian Empire, 1816 - 1821. Per General Thomas Graham in his A Contemporary Account of the 1799 Campaign in Germany and Switzerland, "Masséna caused a bridge to be thrown over the river at Azmooz, opposite the narrow pass of Luciensteig, and marched to that point with 5,000 or 6,000 men".
If I had to guess the bridge was probably built to the left of the arrow and place name of Trubbach.
Graham continues: "The Austrians, though not surprised, yet not having sufficient time to make every preparation for their defense, stood firm. They checked the enemy by a well continued cannonade at Balzers (located east of the top arrow) and near Mayenfeld (off map to the south of Luziensteig in the SE corner of the map), and bravely defended the approach to the Steig". Despite a strong defense the fortifications at St. Luziensteig were taken on the evening of 6 March.
Below is a map excerpt showing Feldkirch in 1797.
The top of the map is not true north. The French advanced eastwards along the red road starting in the top left corner. A good description of both battles for Feldkirch and another map can be found here.